AP_InertialSensor: allow gyro calibration to take up to 30 seconds

this gives time for the user time to get their battery hatches on and
hold the model steady. 5 seconds was just far too short
AP_NavEKF: add another health check in the EKF

if SV, SP and SH are all off then the most likely cause is divergence
of the EKF. This was done based on a flight log with bad gyro cal
Replay: cope with new airspeed log msg
AP_NavEKF: added getStaticMode() function
DataFlash: added staticmode to EKF4 message

useful when diagnosing logs
Create separate pitch/yaw servo types.

In some cases, it makes more sense to have separate types for
position vs. on/off for pitch vs. yaw servos.  For example,
yaw servos on properly designed trackers may not have spin
limits, while pitch servos may.  In this case, you need to
mix the servo types.