Adding support for drag and drop of folders and shortcuts.

also:
- Long press on empty space on workspace now brings up customization tray
- Fixed: while dragging, items appeared to be dropping on folders two cells to the right
- Fixed: Disabling drops on folders when the workspace is shrunken
- Fixed: account for scaling of dragged items when checking if they overlap
          with shrunken workspace screens
- Making folder icons dimmable to match shortcuts and widgets
- When deciding with shrunken workspace screen we're dragging to, we now use the closest screen rather than the one that has been overlapped the most
- Refactored drag/add mechanism, removing array of occupied cells from CellInfo
- Removed dead code/variables

src/com/android/launcher2/LiveFolderInfo.java

@@ -16,6 +16,7 @@
 
 package com.android.launcher2;
 
+import android.content.ComponentName;
 import android.content.ContentValues;
 import android.content.Intent;
 import android.graphics.Bitmap;
@@ -28,6 +29,8 @@ class LiveFolderInfo extends FolderInfo {
      */
     Intent baseIntent;
 
+    ComponentName componentName;
+
     /**
      * The live folder's content uri.
      */