* Apply the default Oreo theme and inherit the layouts
from Google for the Settings app, in order to keep
UI consistency.
* Get rid of SettingsDrawerActivity as it no longer fits in
and include the back button in the action bar.
* Kill the icon drawable not only because is a leftover,
but also doesn't really serve any puropose in the new UI.
Change-Id: I53b6d3bb99d63852ba34d71e16ae99f05223569e
