Ghostery settings: Tracker DB list

[chrmod]

In the Ghostery settings we want to add a new tab called "Tracker DB" - it will be a simple explorer for all Tracker DB entries. Starting with categories, users will be able to list all patterns/organizations present in the tracker db. All info available from Tracker DB repo should be available with exceptions of notes and ghostery_id.

The UI may be similar to Global Tracking list from MV2 settings popup.

[chrmod]

will be implemented as part of #1512