ADT/Layoutlib: Reimplement parts of BitmapFactory

The original bitmap factory is mostly done in native and deals
with the normal android Bitmap class which has been replaced
in the layoutlib by a bitmap that is merely a wrapper around
an AWT BufferedImage.

This new BitmapFactory creates the layoutlib version of
Bitmap all in Java.

Change-Id: Ice8b5d19141a9a43f83349c159201bf85604b3b0