AP_TECS : Add protection for airspeed runaway due to pitch errors
AP_NavEKF : Add low speed magnetometer calibration option
AP_NavEKF : Add sideslip constraint to allow plane flight without magnetometer
AP_NavEKF : update comments
AP_NavEKF : Make all compass use autodetect
AP_NavEKF : enable operation without a compass for planes
AP_NavEKF : improved  static and on-ground mode selection logic
AP_NavEKF : improved on-ground, in-air check and GPS yaw alignment