Revert "SystemUI: Expose heads up."

This reverts commit e745a521dc788ae7ae3d3c900b650443563d50d3.

Conflicts:
	core/java/android/provider/Settings.java
	packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
	packages/SystemUI/src/com/android/systemui/statusbar/BaseStatusBar.java
Revert "Revert "HeadsUp: Add heads up quicksettings tile. (1/2)""

This reverts commit 87b08d8322011ca01ea5fd64b1443ee1831e0e9c.