Quiet Hours: Clean up and consolidate code

- Added: Allow disabling of system sounds

Ported from cm-10.2.

Change-Id: I7d2619becb99c336d23896a672136f491d972abd

Conflicts:
	services/java/com/android/server/NotificationManagerService.java
Add xxhdpi versions of our improved tethering icons

Change-Id: If943f81389774a1f8ca0407cab4756687a273be7
hwui: Apply hwui qcom fixes to all adreno-bearing hardware

Even if the device doesn't fully use the qcom stack, changes to
libhwui are generally workarounds for adreno-specific issues and
apply across the board without other dependencies

Change-Id: I10455ebf09c1d00762b06e3c092398604bb39796