current_loc should be used, not prev_WP_loc

See discussion in issue #1425

take into account trim value in set_radio()

useful when diagnosing logs

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

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

otherwise the user has no opportunity to do a gyro calibration

MissionPlanner sends param1=1 and param3=1 for preflight
calibration. This was having the effect of redoing the accel
calibration as 1D cal on every flight!

the reflect command has not been merged upstream yet

No functional change

fixes issue #1623

thanks to klrill-ka

fixes issue #1622

thanks to klrill-ka

also try to start external ms5611

fixes issue #1617

Also minor format and commenting addition