Added the ability to layer a StateListDrawable over the bitmap.

I was getting sick of using FrameLayouts with my ImageViews and layering a View with a StateListDrawable background on top of it. I did basic testing on this using a GridView. Seems to work fine (a little slower than usual if you provide a resource because the StateListDrawable needs to be parsed), but it seemed like I had to scroll an ImageView off the screen and then back on again to get it to display if it was loaded from the cache. Let me know if you want me to do more intensive testing.