position_estimator_inav: GPS health detection changed, minor improvements
position_estimator_inav: minor fixes
position_estimator_inav: GPS signal quality hysteresis, accel bias estimation fixed, cleanup
position_estimator_inav: more compact messages to fit in mavlink packet
position_estimator_inav: GPS topic timeout detection fixed, messages about GPS signal state in mavlink added
commander: require only valid velocity for EASY mode, allows flying with FLOW and no GPS
position_estimator_inav: major update, using optical flow for position estimation
sensors: slow down updates rate to 200Hz to free some CPU time
position_estimator_inav: major optimization, poll only attitude topic, publish at 100 Hz
Revert "sensors: slow down updates rate to 200Hz to free some CPU time"

This reverts commit 81a4df0953e738041d9fdc2b2eb353a635f3003b.
multirotor_pos_control: track reference position even if not active to handle reference changes properly
multirotor_pos_control: run mainloop at 100Hz
Fixed logging, GPS, and startup scripts.
Added always logging.
First commit of code, very far from being able to compile.
Somewhat working EKF position estimator.