Multi-window support

Change-Id: Ie5860c2105ad9c971157b41d65f8fab337461ef6

Conflicts:
	core/java/android/app/Activity.java
	core/java/android/inputmethodservice/InputMethodService.java
	core/java/android/view/IWindowManager.aidl
	packages/SystemUI/src/com/android/systemui/recent/RecentsPanelView.java
	policy/src/com/android/internal/policy/impl/PhoneWindow.java
	services/java/com/android/server/wm/WindowManagerService.java