Refactor CFX settings for better consistency and ease of use

We have two top level settings headers:

-- Interface
-- System

Their respective target preference screens launch the next
level of preferences where the actual settings are.

-- Interface
   |
   |-- Quick settings
       |
       |-- Static tiles
       |   |
       |   |-- Tile Layout Fragment
       |
       |-- Dynamic tiles (category of checkbox preferences)

This is more consistent with Android settings preference