fix: fixed race condition between http.Server ListenAndServe & Shutdown, now service crash during startup correctly closes http server every time

refactoring: lots of refactoring around server shutdown flows, making sure process is terminated when background service has crashed

* refactoring: metrics package now follows new service interface & registration

* fix: minor fix, make sure metrics service is imported, by grafana-server

Revert "Opportunities to unindent code (unindent)"

[skip ci]

dashboard: show save as button if user has edit permission

This will show the "Save As..." button in dashboard settings page if the user 
has edit permissions (org role admin/editor or viewers_can_edit enabled) 
and has at least edit permission in any folder.

Opportunities to unindent code (unindent)

[skip ci]

Histogram: fix invisible highest value bucket

* wip: start on refactoring settings

* settings: progress on settings refactor

* refactor: progress on settings refactoring

* fix: fixed failing test

* settings: moved smtp settings from global to instance

The table-panel-wrapper class got removed when clicking on the panel
menu which resulted in extra padding for the .panel-content div. This
fixes that by setting the table-specific css class lower down in the
html.

New explore feature overriding css for dropdown typeahead component.

This commit fixes the following unindent findings:
pkg/api/common.go:102:2: "if x { if y" should be "if x && y"
pkg/components/dynmap/dynmap.go:642:2: invert condition and early return
pkg/components/dynmap/dynmap.go:681:2: invert condition and early return
pkg/components/simplejson/simplejson.go:171:2: "if x { if y" should be "if x && y"
pkg/middleware/dashboard_redirect.go:42:3: invert condition and early return
pkg/tsdb/mssql/mssql.go:301:3: invert condition and early break
pkg/tsdb/mysql/mysql.go:312:3: invert condition and early break
pkg/tsdb/postgres/postgres.go:292:3: invert condition and early break
pkg/tsdb/sql_engine.go:144:2: invert condition and early return

Fix golint warnings

This commit fixes the following golint warnings:
pkg/bus/bus.go:64:9: if block ends with a return statement, so drop this else and outdent its block
pkg/bus/bus.go:84:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:137:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:177:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:183:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:199:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:208:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/components/dynmap/dynmap.go:236:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:242:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:257:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:263:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:278:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:284:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:299:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:331:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:350:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:356:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:366:12: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:390:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:396:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:405:12: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:427:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:433:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:442:12: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:459:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:465:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:474:12: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:491:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:497:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:506:12: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:523:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:529:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:538:12: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:555:9: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:561:10: if block ends with a return statement, so drop this else and outdent its block
pkg/components/dynmap/dynmap.go:570:12: if block ends with a return statement, so drop this else and outdent its block
pkg/login/ldap.go:55:11: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/login/ldap_test.go:372:10: if block ends with a return statement, so drop this else and outdent its block
pkg/middleware/middleware_test.go:213:12: if block ends with a return statement, so drop this else and outdent its block
pkg/plugins/dashboard_importer.go:153:11: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/plugins/dashboards_updater.go:39:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/plugins/dashboards_updater.go:121:10: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/plugins/plugins.go:210:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/plugins/plugins.go:235:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/alerting/eval_context.go:111:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/alerting/notifier.go:92:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/alerting/notifier.go:98:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/alerting/notifier.go:122:10: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/alerting/rule.go:108:10: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/alerting/rule.go:118:10: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/alerting/rule.go:121:11: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/alerting/notifiers/telegram.go:94:10: if block ends with a return statement, so drop this else and outdent its block
pkg/services/sqlstore/annotation.go:34:11: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/sqlstore/annotation.go:99:11: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/sqlstore/dashboard_test.go:107:13: if block ends with a return statement, so drop this else and outdent its block
pkg/services/sqlstore/plugin_setting.go:78:10: if block ends with a return statement, so drop this else and outdent its block
pkg/services/sqlstore/preferences.go:91:10: if block ends with a return statement, so drop this else and outdent its block
pkg/services/sqlstore/user.go:50:10: if block ends with a return statement, so drop this else and outdent its block
pkg/services/sqlstore/migrator/migrator.go:106:11: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/services/sqlstore/migrator/postgres_dialect.go:48:10: if block ends with a return statement, so drop this else and outdent its block
pkg/tsdb/time_range.go:59:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/tsdb/time_range.go:67:9: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)
pkg/tsdb/cloudwatch/metric_find_query.go:225:9: if block ends with a return statement, so drop this else and outdent its block
pkg/util/filepath.go:68:11: if block ends with a return statement, so drop this else and outdent its block (move short variable declaration to its own line if necessary)

This commit fixes the following golint warnings:
pkg/api/avatar/avatar.go:229:12: should omit type *http.Client from declaration of var client; it will be inferred from the right-hand side
pkg/login/brute_force_login_protection.go:13:26: should omit type time.Duration from declaration of var loginAttemptsWindow; it will be inferred from the right-hand side
pkg/metrics/graphitebridge/graphite.go:58:26: should omit type []string from declaration of var metricCategoryPrefix; it will be inferred from the right-hand side
pkg/metrics/graphitebridge/graphite.go:69:22: should omit type []string from declaration of var trimMetricPrefix; it will be inferred from the right-hand side
pkg/models/alert.go:37:36: should omit type error from declaration of var ErrCannotChangeStateOnPausedAlert; it will be inferred from the right-hand side
pkg/models/alert.go:38:36: should omit type error from declaration of var ErrRequiresNewState; it will be inferred from the right-hand side
pkg/models/datasource.go:61:28: should omit type map[string]bool from declaration of var knownDatasourcePlugins; it will be inferred from the right-hand side
pkg/plugins/update_checker.go:16:13: should omit type http.Client from declaration of var httpClient; it will be inferred from the right-hand side
pkg/services/alerting/engine.go:103:24: should omit type time.Duration from declaration of var unfinishedWorkTimeout; it will be inferred from the right-hand side
pkg/services/alerting/engine.go:105:19: should omit type time.Duration from declaration of var alertTimeout; it will be inferred from the right-hand side
pkg/services/alerting/engine.go:106:19: should omit type int from declaration of var alertMaxAttempts; it will be inferred from the right-hand side
pkg/services/alerting/notifier.go:143:23: should omit type map[string]*NotifierPlugin from declaration of var notifierFactories; it will be inferred from the right-hand side
pkg/services/alerting/rule.go:136:24: should omit type map[string]ConditionFactory from declaration of var conditionFactories; it will be inferred from the right-hand side
pkg/services/alerting/conditions/evaluator.go:12:15: should omit type []string from declaration of var defaultTypes; it will be inferred from the right-hand side
pkg/services/alerting/conditions/evaluator.go:13:15: should omit type []string from declaration of var rangedTypes; it will be inferred from the right-hand side
pkg/services/alerting/notifiers/opsgenie.go:44:19: should omit type string from declaration of var opsgenieAlertURL; it will be inferred from the right-hand side
pkg/services/alerting/notifiers/pagerduty.go:43:23: should omit type string from declaration of var pagerdutyEventApiUrl; it will be inferred from the right-hand side
pkg/services/alerting/notifiers/telegram.go:21:17: should omit type string from declaration of var telegramApiUrl; it will be inferred from the right-hand side
pkg/services/provisioning/dashboards/config_reader_test.go:11:24: should omit type string from declaration of var simpleDashboardConfig; it will be inferred from the right-hand side
pkg/services/provisioning/dashboards/config_reader_test.go:12:24: should omit type string from declaration of var oldVersion; it will be inferred from the right-hand side
pkg/services/provisioning/dashboards/config_reader_test.go:13:24: should omit type string from declaration of var brokenConfigs; it will be inferred from the right-hand side
pkg/services/provisioning/dashboards/file_reader.go:22:30: should omit type time.Duration from declaration of var checkDiskForChangesInterval; it will be inferred from the right-hand side
pkg/services/provisioning/dashboards/file_reader.go:24:23: should omit type error from declaration of var ErrFolderNameMissing; it will be inferred from the right-hand side
pkg/services/provisioning/datasources/config_reader_test.go:15:34: should omit type string from declaration of var twoDatasourcesConfig; it will be inferred from the right-hand side
pkg/services/provisioning/datasources/config_reader_test.go:16:34: should omit type string from declaration of var twoDatasourcesConfigPurgeOthers; it will be inferred from the right-hand side
pkg/services/provisioning/datasources/config_reader_test.go:17:34: should omit type string from declaration of var doubleDatasourcesConfig; it will be inferred from the right-hand side
pkg/services/provisioning/datasources/config_reader_test.go:18:34: should omit type string from declaration of var allProperties; it will be inferred from the right-hand side
pkg/services/provisioning/datasources/config_reader_test.go:19:34: should omit type string from declaration of var versionZero; it will be inferred from the right-hand side
pkg/services/provisioning/datasources/config_reader_test.go:20:34: should omit type string from declaration of var brokenYaml; it will be inferred from the right-hand side
pkg/services/sqlstore/stats.go:16:25: should omit type time.Duration from declaration of var activeUserTimeLimit; it will be inferred from the right-hand side
pkg/services/sqlstore/migrator/mysql_dialect.go:69:14: should omit type bool from declaration of var hasLen1; it will be inferred from the right-hand side
pkg/services/sqlstore/migrator/mysql_dialect.go:70:14: should omit type bool from declaration of var hasLen2; it will be inferred from the right-hand side
pkg/services/sqlstore/migrator/postgres_dialect.go:95:14: should omit type bool from declaration of var hasLen1; it will be inferred from the right-hand side
pkg/services/sqlstore/migrator/postgres_dialect.go:96:14: should omit type bool from declaration of var hasLen2; it will be inferred from the right-hand side
pkg/setting/setting.go:42:15: should omit type string from declaration of var Env; it will be inferred from the right-hand side
pkg/setting/setting.go:161:18: should omit type bool from declaration of var LdapAllowSignup; it will be inferred from the right-hand side
pkg/setting/setting.go:473:30: should omit type bool from declaration of var skipStaticRootValidation; it will be inferred from the right-hand side
pkg/tsdb/interval.go:14:21: should omit type time.Duration from declaration of var defaultMinInterval; it will be inferred from the right-hand side
pkg/tsdb/interval.go:15:21: should omit type time.Duration from declaration of var year; it will be inferred from the right-hand side
pkg/tsdb/interval.go:16:21: should omit type time.Duration from declaration of var day; it will be inferred from the right-hand side
pkg/tsdb/cloudwatch/credentials.go:26:24: should omit type map[string]cache from declaration of var awsCredentialCache; it will be inferred from the right-hand side
pkg/tsdb/influxdb/query.go:15:27: should omit type *regexp.Regexp from declaration of var regexpOperatorPattern; it will be inferred from the right-hand side
pkg/tsdb/influxdb/query.go:16:27: should omit type *regexp.Regexp from declaration of var regexpMeasurementPattern; it will be inferred from the right-hand side
pkg/tsdb/mssql/mssql_test.go:25:14: should omit type string from declaration of var serverIP; it will be inferred from the right-hand side

Fixes #11758

Explore: add support for multiple queries

* docs: further documents changes to the docker image.
* docs: explains the changes to user id better.

* notification-service-refactor2:
  fix: removed log calls used while troubleshooting
  refactor: refactoring notification service to use new service registry hooks

Explore UI skeleton

* adds +/- buttons to query rows in the Explore section
* on Run Query all query expressions are submitted
* `generateQueryKey` and `ensureQueries` are helpers to ensure each
 query field has a unique key for react.

* refator: refactored PluginManager to be a self registering service, a lot more work needed to fully make plugin manager use instance variables and not so many globals

revert renaming of unit key ppm