Initial OMA DRM forward lock contribution

OMA DRM forward lock agent is plugged into the
Open DRM framework. Forward lock agent implementation contains:
- Forward lock engine to communicate with framework
- Converter to encrypt the original file into a special format
- Decoder to feed the decrypted data for rendering
- Lightweight unique key-encryption mechanism
- Documentation

Change-Id: Id828ebc30b8147b58b14960a73571648bc01ae94