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.
Fix unable to disable GPS home mode via switch.  Fixes #87.
Latest binaries with with for #87.
DISPLAY - Fix ticker updating problem, line buffer was too short.
Update gps.h

Add hdop information in order to display GPS quality signal in telemetry
Update gps.c

Compute GPS quality signal
Update barometer.h

Allow temperature from baro to be used by telemetry
STM32F3 - Cleanup serial port usage.
Insert missing space into version message.
Remove some tabs.
STM32F3 - Remove some compiler warnings.
Allow disabling of I2C for targets that do not use it.
STM32F3 - Add a GPIO alternate function configuration to timer mappings.
Decouple ms5611 baro driver from bmp085 driver.
Disable HMC5883L MAG Data Ready GPIO signal line initialisation except
on naze.

Note: The signal does not appear to be used by the code anyway.
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'
CC3D - Allow building of a binary that is compatible with the OpenPilot
CC3D bootloader to allow easy switching between OpenPilot and
Cleanflight.

Submitted by Alessio Morale -
http://forums.openpilot.org/topic/43569-baseflightcleanflight-ported-to-cc3d/?p=372149
Fix compiler warning when building for non NAZE targets that use the
HMC5883 compass driver.