position_estimator_inav: GPS health detection changed, minor improvements
position_estimator_inav: minor fixes
Merge branch 'master' into inav_fix
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
Merge branch 'master' into inav_fix
Merge branch 'master' into inav_fix
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
Merge branch 'master' into inav_fix
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.
Merge branch 'inav_fix' into inav_flow
position_estimator_inav: code style fixed
position_estimator_inav: avoid triggering land detector on altitude reference changes, don't reset altitude on arming if sonar is valid
multirotor_pos_control: track reference position even if not active to handle reference changes properly
Added vehicle_local_position.ref_surface_timestamp to track surface level changes. Reference altitude updated continuosly when sonar available.
multirotor_pos_control: debug log messages removed