[imp] Add collapsible sidebar. Fixes #4197

Move button before searchbox

Add tooltip

Fix remembering state. Simplify language string.

Layout fixes.

Updated icons, made them state aware. Updated language strings, made them state aware.

Updated icons, alpha ordered language file, added grey background to the sidebar.

Make the code abstract

Added check if localStorage is available. Added code change to compressed core.js.

Added toggle button to all views. Generated CSS files based on less generator.

Fixed toggle buttons on user views. Update template-rtl.less.

Fixed toggle button being activated on enter in filter field.

Moved button to the sidebar file. Added transition changes.

Cleanup banners

Cleanup banners

Further cleanup

Further cleanup

Simplify hiding the sidebar

Keep the button visible

Add missing empty line

Updated the sidepanel. Many thanks to @RemcoJanssen

Fixed Plugin view using the wrong div ID

Updated CSS for RTL languages

Change the icons used for closing and opening.

Updated CSS for RTL.