HIL and fixed wing fixes - gives perfect results in simulation

@thomasgubler Please review for fixed wing changes. @DrTon @julianoes Please review for state machine changes.

This change addresses the following challenges / issues:

  * HIL required a RC previously and also the power module to be connected. Fixed.
  * The HIL voltage was fighting with power module readings. Fixed.
  * Mode switching from QGC completely supported
  * Remains on the restart-mission-from-start feature used previously confused the navigation engine on the first waypoint. Fixed now (found during test flights two weeks ago)
  * Added default gains for a number of fixed wing airframes. Will need more tuning, but should be reasonable.
  * The waypoint switching / reached distance now depends on the L1 distance and airspeed. This makes much smoother transitions.
  * Roll control integrals are reset on exiting circle mode. This is a kind of practical approach, but with good reasons.
  * From tridge: Monitoring of IO rails added.

This has been tested extensively in HIL and should be good to merge. Test flights (in particular on multicopter) would be appreciated.