Kafka alerting

Prometheus client lib support gzip by itself. Which caused the
response to be double gzipped sometimes. We should use the Grafana
middle ware instead.

closes #9464

* added images to annotation docs

* added gifs and png to annotations, minor code formatting fix in alertlist

Bugfix: Always verify TLS unless explicitly told otherwise

initial draft of plugin dev document

* fixed minor styling issus

* fixed code formatting

Merge branch 'verify_datasource_tls' of https://github.com/mattbostock/grafana into mattbostock-verify_datasource_tls

* annotations: add endpoint for writing graphite-like events

* annotations: fix new line handling in tooltip

* annotations: support tags in prior to Graphite 0.10.0 format

You to your typo

Merging upstream

fix: set lastSeenAt date when creating users to then years in past insteasd of empty date, fixes #9260

I renamed `tlsAuth` to `tlsClientAuth` to better describe the fact that
this variable is used to enable TLS client authentication (as opposed to
server authentication) in c04d95f35.

However, changing the name breaks backwards compatibility for existing
installations using this feature and Grafana does not have a
standardised way of migrating changes in the schema:
https://github.com/grafana/grafana/pull/9377#issuecomment-333063543

For reasons of expediency given the severity of the bug (not verifying
TLS), keep the old name.

It's an acronym, so it should be all caps.

In c04d95f35 I changed the default for datasource HTTP requests so that
TLS is always verified.

This commit adds a checkbox to allow an admin to explicitly skip TLS
verification, for testing purposes.

URL is an acronym, it should be all caps.

...to make this file compatible with goimports:
https://godoc.org/golang.org/x/tools/cmd/goimports

* add postgresql datasource

* add rest of files for postgres datasource

* fix timeseries query, remove unused code

* consistent naming, refactoring

* s/mysql/postgres/

* s/mysql/postgres/

* couple more tests

* tests for more datatypes

* fix macros for postgres

* add __timeSec macro

* add frontend for postgres datasource

* adjust documentation

* fix formatting

* add proper plugin description

* merge editor changes from mysql

* port changes from mysql datasource

* set proper defaultQuery for postgres

* add time_sec to timeseries query
accept int for value for timeseries query

* revert allowing time_sec and handle int or float values as unix
timestamp for "time" column

* fix tslint error

* handle decimal values in timeseries query

* allow setting sslmode for postgres datasource

* use type switch for handling data types

* fix value for timeseries query

* refactor timeseries queries to make them more flexible

* remove debug statement from inner loop in type conversion

* use plain for loop in getTypedRowData

* fix timeseries queries

* adjust postgres datasource to tsdb refactoring

* adjust postgres datasource to frontend changes

* update lib/pq to latest version

* move type conversion to getTypedRowData

* handle address types cidr, inet and macaddr

* adjust response parser and docs for annotations

* convert unknown types to string

* add documentation for postgres datasource

* add another example query with metric column

* set more helpful default query

* update help text in query editor

* handle NULL in value column of timeseries query

* add __timeGroup macro

* add test for __timeGroup macro

* document __timeGroup and set proper default query for annotations

* fix typos in docs

* add postgres to list of datasources

* add postgres to builtInPlugins

* mysql: refactoring as prep for merging postgres

Refactors out the initialization of the xorm engine and the query logic
for an sql data source.

* mysql: rename refactoring + test update

* postgres:refactor to use SqlEngine(same as mysql)

Refactored to use a common base class with the MySql data source.

Other changes from the original PR:
- Changed time column to be time_sec to allow other time units in the
future and to be the same as MySQL
- Changed integration test to test the main Query method rather than
the private transformToTable method
- Changed the __timeSec macro name to __timeEpoch
- Renamed PostgresExecutor to PostgresQueryEndpoint

Fixes #9209 (the original PR)

* postgres: encrypt password on config page

With some other cosmetic changes to the config page:
- placeholder texts
- reset button for the password after it has been encrypted.
- default value for the sslmode field.

* postgres: change back col name to time from time_sec

* postgres mysql: remove annotation title

Title has been removed from annotations

* postgres: fix images for docs page

* postgres mysql: fix specs

* graph: fix NaN formatting, #9012

* singlestat: prevent null value coloring, #9012, #8404

* timeseries: add tests for #9012 and move test file to TS

exclude dashboard field from snapshot list search