Reimplement expanded desktop on top of immersive mode.

Change-Id: I8ed08afebef0bb08a2694b1dbdd6dd1887b5b065

Conflicts:

	core/java/android/provider/Settings.java
	core/java/android/view/WindowManagerPolicy.java
	core/res/res/values/symbols.xml
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
	services/java/com/android/server/wm/WindowManagerService.java