Code allowing the use of sonar without requiring a barometer.

This code has been flight tested on a Naze32 acro, with no barometer onboard.  It also works when the target doesn't have BARO defined.
Merge branch 'feature-sonar-flight-mode-no-baro' of dclifton-github.com:nebbian/cleanflight into nebbian-feature-sonar-flight-mode-no-baro

Fixed tabs, kept old references to VARIO.  Made SONAR mode a new option so that aux settings could be preserved.

Conflicts:
	src/main/config/runtime_config.h
	src/main/flight/altitudehold.h
	src/main/flight/imu.c
	src/main/io/rc_controls.h
	src/main/mw.c
	src/main/sensors/initialisation.c
Bump config version for new SONAR flight mode.
Merge branch 'nebbian-feature-sonar-flight-mode-no-baro'