Multi-window support

Change-Id: I9b3d737ba7efa4d3677baec18edf3eb36d49ba14

Conflicts:
	core/java/android/app/Activity.java
	core/java/android/app/IActivityManager.java
	packages/SystemUI/res/values-zh-rCN/mk_strings.xml
	packages/SystemUI/res/values/mk_strings.xml
	packages/SystemUI/src/com/android/systemui/recent/RecentsPanelView.java
	services/java/com/android/server/am/ActivityStack.java