[2/2] SystemUI: Add brightness slider to notification drawer
adds a brightness slider below the expanded statusbar header and
(if enabled) quick settings ribbons

Change-Id: If025fd84fa2dcaacbd4a12039eea7d37ba5b82d8
Settings: allow ribbons to be configured

code side was there already, seems it just got forgotten in the xml

Change-Id: I7ff5488cc3b53ce9785c3e46effcf29dc31fe0ef