Adding enable/disable option for sendCommand()

- Added enum CAMERA_CMD_ENABLE_SHUTTER_SOUND which corresponds to
  command type for enabling/disabling shutter sound.
- The implementation checks if it is legal to disable shutter sound.
  If it is, then any process can disable the sound. If not, then only
  the mediaserver process is allowed to do this. Currently time lapse
  capture needs this functionality to disable shutter sound when still
  mode is used to capture time lapse video.

Change-Id: Id147a3bcc6a345c2c6a6d52bf98fd8292386bb19