[rotorcraft] only go to HOME mode if in NAV

then you don't have this "failsafe" in manual modes anymore,
but it will prevent issues like #850
[gen_settings] fix bug when target is not specified (use default list)
[gen_settings] only check targets on makefile nodes
[ins] hack float_invariant to support geo_mag module

closes #858 until we have a proper solution of publishing local magnetic field via ABI messages
[ardrone2] add rm_dir command
[ardrone2] send filter status from navboard

- it allows to see if the mag is crashed or not
- set a max retry on the reset PIC board hack (which doesn't seems to
  help anyway)
[module] add agl_dist module
[math] fix polyfit init
[airframes] fix quad_navgo actuators for nps
New joystick file for RC trainer
[modules] Added temperature adc module

Added temperature driver for analog sensors (LM35 and 100k NTC)

closes #857
[modules] add airspeed_ms45xx_i2c module

- differential pressure is filtered with a butterworth lowpass
- including (persistent) settings for pressure scale and offset
- add AIRSPEED_MS45XX message

closes #852
[modules] ms45xx publishes BARO_DIFF and TEMPERATURE via ABI