Adding a constructor to CacheableBitmapDrawable.java to let it implement the default (non deprecated) constructor with Bitmap parameter.

This constructor is needed because the only one implemented for now is based on a deprecated one. The current constructor does not handle the screen/bitmap density scaling (Resources parameter). That can cause differences on bitmap rendering for this drawable.

Side effect, by using an init method to initialize the variables, I had to remove the final attribute to mUrl and mRecyclePolicy.