Settings: Search all settings

[Innders]

First step in better filtering of settings is to do a settings wide (all addons) search. From that the user can then move onto the second step of filtering the search results.

This PR will only handle the first step of searching.

• Search matches, field names, values and descriptions (basically everything).
• Big search bar at the top of the page.
• When searching remove the selection of addons in the left panel and search through all addons.
• If an addon is selected in the left panel then the search becomes filtered to only the selected addons.