Gallery2 : Uses internal Drm image decoder api in Gallery app

- Remove all previous drm implementation which is basically uses
  base bitmap decode apis to decode drm image files.
- Introduced new hidden apis on BitmapFactory and
  BitmapRegionDecoder specific to DRM content which
  is more practical to DRM framework.
- Uses DrmHelper a utility drm api library to code reusability.
- This approch will fix the issue on sharing images from
  Third party application.

CRs-fixed : 804191

Change-Id: I2e9489800c57df4fdeeb21f1548fbccc6dfbd3f9