Realtime drop area

Bug: 10686781

Improved also the scroll on drag-n-drop and NOTE ALSO

- The animations are not in, neither the lift up nor drop in
- Pos >= 20 is not draggable, nor droppable
- The implementation of D-N-D may need a refactor
- The refactor will use the ListView as the only D-N-D handler
- The refactor will remove the drag handleer from individual row
- The refactor will make it possible to do animation on the drag shadow

Change-Id: Ic7c81a9a139eb46ef1820192528da14e5d8e52cb