Add 2 APIs (suspend/resume) in MediaPlayer

- API:suspend() will just pause the player and release all the decoders
  to replace release() which will release the whole player
- API:resume() will just init the decoders again,
  then start() will be called to start to play the streaming

Change-Id: I3e2ffeb50dfe6d156b18416fa8964ff4a3d56a2c