Add SystemAudioAction(FromAvr|FromTv).

The system audio can be initiated by Tv itself or by AVR through
<Set System Audio Mode> CEC message.

This CL also includes:
- Add HdmiConstants, HdmiUtil class to handle various constants and
  utility functions.
- Add default message dispatcher to all queued actions.
- Add an argument on HdmiControlService.removeAction(class) to prevent
  from removing the caller itself.

Change-Id: I9fd9089bed876f04b58c483879b64edfae94a298