Tracker: use handle_set_mode()
AntennaTracker: notify armed after receiving vehicle position
AntennaTracker: minor comment and format fix
Tracker: process mavlink msgs from vehicle once

previously heartbeat messages from the vehicle could be processed twice.
Once at the top of hte handleMessage function where they were forwarded
onto the GCS and then again lower down in the function where all
received heartbeats were sent to the vehicle.
Tracker: GCS_Mavlink format fix-up of indentation
Tracker: remove forwarding of pos and pressure to vehicle