Base: implement Floating window multitasking

access from app circle sidebar
MoveAble window
ResizeAble window (using pinch multitouch)
Multitasking
fix build
Auto resize when snapping to TOP, BOTTOM, LEFT, RIGHT
based from xhalofloatingwindow by @zst123
fix scaling calculation for layout
cleanup whitespace

Change-Id: Iad00c239de7d66e8bb45205ce626d4f08417b7cd

Conflicts:
	core/java/android/app/Activity.java
	core/java/android/app/ActivityThread.java
	core/java/android/app/IActivityManager.java
	core/java/android/content/Intent.java
	core/java/android/view/IWindowManager.aidl
	packages/SystemUI/res/values/custom_strings.xml
	services/java/com/android/server/am/ActivityRecord.java
	services/java/com/android/server/am/ActivityStack.java
	services/java/com/android/server/wm/WindowManagerService.java