ref #9476

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.