Adding a couple memory optimizations to Launcher

-> Always dispose of widget page views when leaving the activity.
   These pages hold onto many bitmaps.
-> Clear database cache when leaving the activity.

Bug: 17967108
Change-Id: I10ebaaed14e7cd86f09a9afcabd73043705f21b8

src/com/android/launcher3/AppsCustomizePagedView.java

@@ -1476,7 +1476,9 @@ public class AppsCustomizePagedView extends PagedViewWithDraggableItems implemen
         }
     }
 
+    @Override
     public void reset() {
+        super.reset();
         // If we have reset, then we should not continue to restore the previous state
         mSaveInstanceStateItemIndex = -1;