Revert "[WIP] Multi-window"

This reverts commit 39e5f03698a46ec8d744db92f86e305eee7dc4d8.

Conflicts:
	core/java/android/app/Activity.java
	core/java/android/view/IWindowManager.aidl
	packages/SystemUI/res/values/ose_strings.xml
	services/java/com/android/server/wm/WindowManagerService.java