Fix megacheck issues

[skip ci]

fix panel solo size

Fix doc error for DingDIng alert

Update the regex-matching in templateSrv to work with the new variabl…

Fix cannot receive dingding alert when alert message is empty

[skip ci]

[skip ci]

[skip ci]

Delete provisioning meta data when deleting Folder

prior to this fix Grafana didnt delete meta data
about the provisioned dashboard in `dashboard_provisioning`
which means that the dashboard wasn't inserted into
Grafana again if the folder was delete within Grafana.

closes #13280

Update the regex-matching in templateSrv to work with the new variable-syntax and be more flexible to regex-changes #13804

Explore: fix graph resize on window resize

[skip ci]

[skip ci]

Fix click-based selection of typeahead suggestion

- resize HOC wrapper only resized first child which in case of large
  graphs was the warning button
- moved warning button inside the panel parent

Explore: query transactions for faster result display

* stackdriver: add resource type to filter and group bys

* stackdriver: remove not used param

* stackdriver: refactor filter and group by code

* stackdriver: remove resource type if its already in filter list

* stackdriver: remove debug logging

* stackdriver: remove more debug logging

* stackdriver: append resource type to legend name if there are more than one type present in the response

* stackdriver: only make new request if filter has real value

* stackdriver: format legend support for resource type

* stackdriver: add resource type to documentation

* stackdriver: not returning promise from query function

* stackdriver: fix refactoring bug

* stackdriver: remove not used import

[skip ci]

See,
$ gometalinter --vendor --deadline 10m --disable-all --enable=megacheck ./...
pkg/tsdb/stackdriver/stackdriver.go:171:26:warning: regular expression does not contain any meta characters (SA6004) (megacheck)

I found this article benchmarking Replace vs Regexp,
https://medium.com/codezillas/golang-replace-vs-regexp-de4e48482f53

See,
$ gometalinter --vendor --deadline 10m --disable-all --enable=megacheck ./...
pkg/tsdb/graphite/graphite.go:167:28:warning: regular expression does not contain any meta characters (SA6004) (megacheck)
pkg/tsdb/graphite/graphite.go:172:28:warning: regular expression does not contain any meta characters (SA6004) (megacheck)

See,
$ gometalinter --vendor --deadline 10m --disable-all --enable=megacheck ./...
pkg/login/ldap.go:188:40:warning: should omit comparison to bool constant, can be simplified to !*extUser.IsGrafanaAdmin (S1002) (megacheck)

Another fix for kiosk mode handling

Kiosk mode url fix

Existing querying was grouped together before handed over to the
datasource. This slowed down result display to however long the slowest
query took.

- create one query transaction per result viewer (graph, table, etc.)
  and query row
- track latencies for each transaction
- show results as soon as they are being received
- loading indicator on graph and query button to indicate that queries
  are still running and that results are incomplete
- properly discard transactions when removing or changing queries