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
AP_NaVEKF : Enable operation without airspeed and compass
AP_NavEKF : increased useage of helper functions
autotest: fixed valgrind options to sim_arduplane.sh
PX4: make compass calibrate fail non-fatal

until we sort out what is going on with compass calibration failures
this is the best option
GCS_MAVLink: allow for proxying of larger MAVLink messages on PX4

this makes it possible to deal with large MAVLink messages
DataFlash: return number of logs as zero correctly 

when we have no file based logs, report no logs :)
GCS_MAVLink: send a "zero logs" message when no logs available
autotest: fixed multi-instance support
autotest: initial version of a antenna tracker simulator
autotest: added -T option to sim_arduplane.sh

starts an antenna tracker
AntennaTracker: fixes for antenna tracker

- use pressure to calculate vehicle altitude
- changed approach to slewing
- fixed mavlink mode
AntennaTracker: added a note on simulating an antenna tracker