vehicle hal further clarification / HVAC update

vehicle hal further clarification / HVAC update

- added HVAC_POWER_ON property
- added special INT / FLOAT OUT_OF_RANGE values for
  max / min / off state
- added dump call for debugging: necessary for debugging
- clarified subscribe behavior for ON_CHANGE type
  VNS will make additional get call for checking initial
  state.
- added clarification on possible -EAGAIN for set call
- added mute flag to allow muting radio from android

bug: 27721415
bug: 28022648
bug: 27971383
bug: 27971578

Change-Id: Ie9a7334b86ab53174b91a4dc651fd87ca17af3d9