Fixes #15505

Fixed navbar backbutton padding

[wip]Cleaning up the theme .scss files 

Updated explore icon and style tweaks

Fixing array direction, adding simple render test

Lowered icon size and improved paddings, tried to align placement between dashboard and explore

Fixed unit test and updated gauge
Added migration for threshold order

Datasource docs for Loki

cli: chmod 755 for backend plugin binaries

Fixes #15477

Fixes #15500. Does a simple filename check if the binary names ends
with _linux_amd64 or _darwin_amd64 then sets the file mode to 755.

Add Lux to units

Remove maxDataPoints and interval props from props to remember in panel model

Changed how react panels store their options

* Added a ReactPanelPlugin as the interface that react panels export, this way react panels have clearer api, and gives us hooks to handle migrations and a way for panel to handle panel changes in the future
* Moved gauge value options into a sub oject and made editor more generic, will be moved out of gauge pane later and shared between singlestat, gauge, bargauge, honecomb
* Also remove nested options prop that was there due to bug
* Added missing Gauge props
* Fixed gauge issue that will require migration later and also value options editor did not handle null decimals or 0 decimals
* Fixed unit tests
* More fixes for react panels

Removed primary class from Add Query button, and changed name of panel options tab

Fix typo in view mode cycle button

Removed primary class from Add Query button, and changed name of Panel Options tab o General Options

- adds Loki data source docs to Grafana docs
- moved query-related docs from Explore to Loki

Added enable_gzip documentation (#15322)

Fixed issue with PanelHeader and grid-drag-handle in fullscreen

fixes #15479