Align queries to prometheus with the step

* origin/master: (21 commits)
  docs: removes notes about beeing introduced in 5.0
  lock caniuse-db version to resolve phantomjs rendering issue
  Update dashboard_permissions.md
  move database-specific code into dialects (#11884)
  refactor: tracing service refactoring (#11907)
  fix typo in getLdapAttrN (#11898)
  docs: update installation instructions targeting v5.1.2 stable
  changelog: add notes about closing #11862, #11656
  Fix dependencies on Node v10
  Update dashboard.md
  changelog: add notes about closing #10338
  Phantom render.js is incorrectly retrieving number of active panels (#11100)
  singlestat: render time of last point based on dashboard timezone (#11425)
  Fix for #10078: symbol "&" is not escaped (#10137)
  Add alpha color channel support for graph bars (#10956)
  interpolate 'field' again in Elasticsearch terms queries (#10026)
  Templating : return __empty__ value when all value return nothing to prevent elasticsearch syntaxe error (#9701)
  http_server: All files in public/build have now a huge max-age (#11536)
  fix: ldap unit test
  decrease length of auth_id column in user_auth table
  ...

* only increase interval by step if jitter happened
* shift both start and end
* simplified tests by using low epoch numbers

resolve phantomjs rendering in production build

For some reason a newer version of this sub-dependency makes phantomjs
rendering unable to generate and save a png image, however without
any error message logged

docs: update dashboard_permissions.md

miss { in repsponse

[skip ci]

Adding a user in a specified organisation uses the admin API

Fix dependencies on Node v10

Update dashboard.md

[skip ci]

Fixes #11099

* singlestat: render time of last point based on dashboard timezone

* changelog: add note for #10338

Fix for #10078: Render value as link in Table panel: ampersand symbol "&" is not escaped in link URL, resulting URL is wrong.

* Set fillColor in bars on load and on color change

* Change bar fill color on color override

* Added test for series overrides

* Moved bars fill color setting into time_series. Fixed issue with prev commit where you could not show bars because of series overrides.

* interpolate 'field' again in Elasticsearch terms queries

Fix for #8662 which was regressed in commit e4950c2d (the field 'field' was no longer interpolated)

* remove unnecessary check for existence of field 'field'

Templating : return __empty__ value when all value return nothing to prevent elasticsearch syntaxe error (#9701)

decrease length of auth_id column in user_auth table

* ldap: case-insensitive LDAP group comparison

According to RFC2251 4.1.5, LDAP strings are case-insensitive. Disregard case when comparing group mappings.

* ldap: add test for case-insensitive group mapping

[skip ci]

fix XSS vulnerabilities in dashboard links

Merge branch 'feature/save_json' of https://github.com/jereksel/grafana into jereksel-feature/save_json