Settings headers and CFX fragments refactor v1.0

Summary:
-- bring back Interface and System headers, while keeping theme compliance
-- Bring back our icons!
-- Move DPI Wizard to System
-- Move Buttons under Display

Test Plan: It works. Ongoing WIP.

Reviewers: synergy, anders3408, jriordan001, raymanfx, donald.munn, rlasalle15

Differential Revision: http://review.codefirex.com/D395