Revert "[WIP] Multi-window"

This reverts commit 1bbd27f0d613b67249ea60b9b0da40e017914723.

Conflicts:
	core/java/android/view/IWindowManager.aidl
	packages/SystemUI/res/values/liquid_strings.xml
	packages/SystemUI/src/com/android/systemui/recent/RecentsPanelView.java
	services/java/com/android/server/am/ActivityStack.java
	services/java/com/android/server/wm/WindowManagerService.java