[tools] gen_modules_doc: update wiki url
[dox][mcu_periph] document some more stuff
update excludes in Doxyfile

and prevent copied chibios file to add doxygen groups
[airborne] remove unused agl and alt_vfilter

alt_vfilter is basically the same as ins/vf_float
[server] add airspeed data in FLIGHT_PARAM message
[server] send negative value if no airspeed available

on a second thought it is safer to tell that there is no airspeed data,
ground speed is already available in the message anyway
[server] change again airspeed field position

for compatibility with PPRZonDroid beta version
[rotorcraft] rc setpoint handling refactored

closes #684 which partially solves #599
[mission] add support for global coordinates in mission module
[ext] update libopencm3
[stm32] update libopencm3 includes

don't explicitly include f1 headers, rather just the generic stm32 ones which will then include the correct ones depending on which familiy is defined
[ext] update luftboot to get libopencm3 include fixes
[rotorcraft] add a HOME mode

similar to HOME mode in fixedwing firmware.
[rotorcraft] go to FAILSAFE mode after 1.5*MAX_DIST_FROM_HOME

In failsafe the rotorcraft should perform a landing which makes more sense than KILL.
You can still set KILL_AS_FAILSAFE to kill instead.
[rotorcraft] add UNLOCKED_HOME_MODE
[gcs] connect the 'back to nav' strip button

also remove some warnings since it seems to be more confusing than
inactive buttons in the strip
[failsafe] settable failsafe mode

- failsafe mode when aircraft is really to far can be set
- descent speed in failsafe mode can be set
- choose more realistic values for max_dist_from_home in default FP
[rotorcraft] add RC_LOST_MODE