[math] fix typo
[fixedwing] move nav.[ch] to firmwares/fixedwing
[conf] remove jsbsim from microjet, add krooz_quad to tests
[rotorcraft] nav approaching_time implemented
[rotorcraft] nav approaching resolution updates

The minimum horizontal distance to wp in order to mark as arrived can be changed by defining
ARRIVED_AT_WAYPOINT
which defaults to 3m.