SysUI: Don't recreate controllers.

The various controllers, such as mLocationController, get recreated
every time the status bar is recreated due to a theme change.  We
should only need to create these if they are null, otherwise use
the controller as is.  Also, each of these controlers registers
themselves as a broadcast receiver and are never unregistered before
recreating them.

Change-Id: I6215aae5a82b7ced8f0f25cf592a804d38825260
Modified "Empty button" > "Leave empty"

"Empty button" implies a placeholder button, which could be confusing to new users.

Change-Id: I092bdb0c8d3cfad79560526f383cdb7efb730a06
Merge "Modified "Empty button" > "Leave empty"" into cm-11.0
Merge "SysUI: Don't recreate controllers." into cm-11.0
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_frameworks_base into temp