[nps] Started to add fixed wing support in NPS
[mission] add mission messages
[mission] add mission module (only parsing messages for now)
[mission] define mission structures
[mission] forgot some files
[rotorcraft] improve in_flight detection heuristic

Simply checks if thrust, speed and acceleration are above a threshold.
Does not rely on RC thrust command anymore, but only on actual thrust command.
Not tested on real vehicle at all so far...

Attempt to improve issue #201 and replaces #468
[nps] A few more NPS for FW updates

 * tweaked FBW for USE_NPS, not SITL
 * Better support for AP or FBW or both
 * added start of a subsystem makefile
[flight_plan] add 'until' attribute to 'survey' and 'call' statement
[flight_plan] update DTD for until attribute with call and survey
[fixedwing] energy_ctrl: don't keywords reserved in c++
[modules] light only for ap
[modules] only use sim_air_speed if not using NPS

for now...
[fixedwing] gps for nps sim
[fixedwing] cleanup autopilot makefile a bit
[fixedwing] ahrs and ins subsystems for nps target
[nps][fixedwing] updates for fixedwing support in NPS
[nps] minor cleanup
[rotorcraft] set guidance_v_zd_sp to zero in altitude hold for visualization
[math] add FLOAT_QUAT_OF_ORIENTATION_VECT
[rotorcraft][guidance][stabilization] quat setpoint fixes

Don't pretend that the commands from guidance_h are actually real euler angles.
Compose a roll/pitch quaternion from simultaneous rotation of roll/pitch,
then rotate around resulting body z-axis to align the heading.

This should "fix" the setpoint passed to the attitude stabilization if in HOVER or NAV
at large angles.
Only tested quickly in simulation...