Make immersive tile a dual tile

front tile always toggles between immersive off and last used immersive state.
back tile switches between states like the old tile did.

Conflicts:
	packages/SystemUI/res/values/pa_strings.xml
	packages/SystemUI/src/com/android/systemui/statusbar/phone/QuickSettings.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/QuickSettingsModel.java