position_estimator_inav: parameters descriptions added
Merge pull request #1214 from PX4/inav_params_descr

position_estimator_inav: parameters descriptions added
commander: Do not confuse developers with wrong comments, do not confuse users with not at all helpful "general error" messages.
Do not confuse operators / users with technical error messages
commander: Explain sensor arming fail case to users
Commander: Print technical feedback as last resort if no feedback was provided before
Merge pull request #1216 from PX4/arming_feedback

Arming feedback
WIP, datalinkloss: implementing basic behavior
Merge remote-tracking branch 'upstream/master' into obcfailsafe
Merge remote-tracking branch 'upstream/obcfailsafe' into obcfailsafe