Status bar brightness control

+ added some fixes to original implementation (thanks mostly cm for that)
+ add multiuser support

Change-Id: Ibc5cc15a9b43eade73670d308d5cc788c93b6210

Conflicts:
	core/java/android/provider/Settings.java

Conflicts:

	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java