updated Workspace thumbnail behavior

- in All Apps mode, fade thumbnails completely
- while dragging, have thumbnails re-appear
- while dragging, give screen thumbnails that can accept drops a different appearance (green outline instead of blue)

Change-Id: I72ddf8a0f1947d35ef11514b7d4eea9ae5eee6e2
diff --git a/src/com/android/launcher2/AllAppsPagedView.java b/src/com/android/launcher2/AllAppsPagedView.java
index b392959..cbb46e2 100644
--- a/src/com/android/launcher2/AllAppsPagedView.java
+++ b/src/com/android/launcher2/AllAppsPagedView.java
@@ -224,6 +224,7 @@
         ApplicationInfo app = (ApplicationInfo) v.getTag();
         app = new ApplicationInfo(app);
 
+        mLauncher.getWorkspace().onDragStartedWithItemSpans(1, 1);
         mDragController.startDrag(v, this, app, DragController.DRAG_ACTION_COPY);
         return true;
     }
@@ -234,6 +235,7 @@
         if (target != this) {
             endChoiceMode();
         }
+        mLauncher.getWorkspace().onDragStopped();
     }
 
     @Override