position_estimator_inav: don't ignore flow if sonar is invalid
navigator: added offboard mode
commander: hack to get velocity offboard control working
mavlink: hack to get the right flow orientation in
mavlink: only save a offboard_control, don't publish to setpoint topics (let the navigator do this)
offboard_control_setpoint: armed does not make sense there
position_setpoint_triplet: add local position and velocity setpoints
mc_pos_control: read velocity setpoints form offboard control and do position offset control