Enabling accessibility drag and drop in folder

> Moving DragAndDropAccessibilityDelegate to a separate class
> Using getFocusedVirtualView() instead of using DownX and downY
> Updating various accessibility strings

Bug: 19776741

Change-Id: I85c2551d4d6172c30702e68f41b114bb999655b6
diff --git a/src/com/android/launcher3/DropTarget.java b/src/com/android/launcher3/DropTarget.java
index c5cca3b..3628e57 100644
--- a/src/com/android/launcher3/DropTarget.java
+++ b/src/com/android/launcher3/DropTarget.java
@@ -183,6 +183,8 @@
      */
     boolean acceptDrop(DragObject dragObject);
 
+    void prepareAccessibilityDrop();
+
     // These methods are implemented in Views
     void getHitRectRelativeToDragLayer(Rect outRect);
     void getLocationInDragLayer(int[] loc);