Multi-Window extension: notifications (original draft by PA)

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/ShortcutsWidget.java
Added toggle for multi-window in notification shade

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/BaseStatusBar.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/ShortcutsWidget.java