broadcast radio API

Initial implementation of system APIs for broadcast
radio framework. Added manager and interfaces to control
a broadcast radio function exposed by the radio HAL.

- RadioManager: contains data structures and definitions as well as
top level API for feature discovery and tuner interface instantiation.
- RadioTuner: interface to control a broadcast radio tuner.
- RadioModule: framework component implementing the RadioTuner interface
and controlling a HW radio module via the radio HAL.
- RadioMetadata: representation of radio meta data (Station name, PTY,
song title, artwork, etc...) communicated by the framework to the client.

Change-Id: Iee42a185c694503e25f0b2dcfa417d88f5e9549b