"BitMatrix to Bitmap"-Writer, to easily display generated QR-Codes in Android applications

The javase module has a `MatrixToImageWriter` for creating displayable BufferedImages for Swing applications. The android-integration module misses this capability.

So, this is a "port" of the mentioned writer for Android, by using Androids `Bitmap`-class, instead of the (in Android not available) BufferedImage class.