[barometer] Removed all USE_BAROMETERs from main, added a dummy baro_board source file and added a BaroEvent that does nothing for the SDK which does not use a baro_boar file.
Merge branch 'ardrone_to_master' of github.com:RoboticaTUDelft/paparazzi into ardrone_to_master

Conflicts:
	sw/airborne/boards/ardrone/baro_board_dummy.c