Adds docs for the new API endpoints, and for the dashboard history feature.

Merge branch 'refactor-basic-diff' of https://github.com/walmartlabs/grafana into walmartlabs-refactor-basic-diff

* dashboard: don't override timezone if default selected, issue #8503

* dashboard: hide UTC icon immediately after timezone changing

Fixes #8656 and properly sets the email_sent and email_sent_on fields
for a tempuser (signup user).

* heatmap: fix incorrect time for UTC timezone, fixes #8706

* heatmap: fix tests for time format

* histogram: don't cut negative values, issue #8628

* histogram: add percent/count option

* histogram: add tests for values normalizing

* histogram: improved ticks rendering

* histogram: fix default value in axes editor

Closes #8717

* table_panel: add option for preserving text formatting

* table_panel: fix undefined style error

* table_panel: fix class adding (add space before 'class')

* table_panel: aligin Type options labels

This should close the issue #8695

Implements feature request #8682

fixes #8655

This changes the css to handle overflow of the string on the input fields.
If an overflow happends an ellipsis is used.

* Fix timeInterval for mysql datasource

This changes the > to >= and the < to <=, so the intervals are inclusive.
This should fix the #8635

* Fix validation