Manage: Disable tabindex in nested buttons
Manage: Fix homepage link alignment
Manage: Make entry actions keyboard navigatable
Manage: Add search help accessibility
Msgbox: Save and restore focus
Manage: Fix delete confirmation cancel
Manage: Make history button accessible
Manage: Make favicons dropdown accessible
Manage: Prevent focus on hidden textarea
Msgbox: Stop tabbing outside of msgbox
Usercss: Make nondefault reset accessible
Usercss: Make colorpicker accessible
Edit: Disable tabindex in nested buttons
Edit: Make info and config icons accessible
Options: Cleanup HTML
Options: Make advanced toggle accessible
Edit: Fix issues popup
Edit: Remove link underlines from icons
also:
* simplified CSS selectors where possible
* .config-name = var name, 1st element in <label>
* .config-value = var value, 2nd element in <label>
* .nondefault class added on <label>
* same icon in manager
(didn't change the editor config icons as those aren't for usercss)
* "external" icon for USO styles to avoid confusion
(opening a tab is an extremely different action)
* smaller paddings in popup
* removed hover effect on label text
(necause native <select> elements cannot be expanded from js)
* various fixups
* don't close on clicking "save" to allow continuous tweaking
* dirty item's label is marked with * and switches to italic
* "save" button is enabled when some value differs from saved
* "use default" button is enabled when some value differs from its default
* "close" becomes "cancel" when there are unsaved changed values
