Fix misspelled authentication in Auth overview doc

Don't use unnest in queries for redshift compatibility

Explore: Fix click to filter for recording rule expressions

- recording rule names contain ':'
- include this in the pattern for metric names

Fix megacheck issues

$ gometalinter --vendor --disable=all --enable=megacheck --deadline=10m ./...
pkg/tsdb/elasticsearch/client/client.go:147:13:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)
pkg/tsdb/elasticsearch/client/client.go:190:14:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)
pkg/tsdb/elasticsearch/client/client.go:218:13:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)

$ gometalinter --vendor --disable=all --enable=megacheck --deadline=10m ./...
pkg/plugins/dashboards_updater.go:51:2:warning: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013) (megacheck)

$ gometalinter --vendor --disable=all --enable=megacheck --deadline=10m ./...
pkg/services/sqlstore/alert_notification.go:242:3:warning: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013) (megacheck)

disable codecov

removes unused files

Fix setting test

ref #11433

moves files from /tests to more appropriate folders

Moves docker/ to devenv/docker

Explore: Add multiline syntax highlighting to query field

* brian2222-patch-1:
  removes testdata from getting started
  Update getting_started.md

ref #11433

Internal metrics: starts counters at zero

annotations: allows template variables to be used in tag filter

Add documentation for postgres query builder

Fix some megacheck issues

ref #11433

Team member labels

list of datasources updated in section: dashboards, panels, the buildingblocks of grafana...

See,
$ gometalinter --vendor --disable-all --enable=megacheck --disable=gotype --deadline 6m ./... | grep ID
alert.go:193:15:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
alert.go:252:18:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
annotation.go:113:12:warning: sess.Table("annotation").Id is deprecated: use ID instead  (SA1019) (megacheck)
org.go:136:24:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
org.go:169:16:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
org_users.go:24:21:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
org_users.go:88:12:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
org_users.go:141:21:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
plugin_setting.go:103:12:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
preferences.go:97:12:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
quota.go:119:17:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
quota.go:221:17:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
team.go:77:24:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
user.go:243:16:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
user.go:267:13:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
user.go:282:13:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
user.go:313:12:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
user.go:475:3:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
user.go:479:13:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)
user.go:493:13:warning: sess.Id is deprecated: use ID instead  (SA1019) (megacheck)