hmc5883: added option for bottom mounted sensors
pios_hmc5883: removed unnecessary read of CTRLB to get the sensor gain
quanton: use proper i2c adapter ids instead of MAIN / FLEXI port macros
quanton: add support for magnetometer on external i2c
pios_hmc5883: removed PIOS_HMC5883_HAS_GPIOS
pios_hmc5883: added support for operation without irq
pios_hmc5883: removed duplicate creation of data_ready_sema
quanton: handle returnvalue from PIOS_HMC5883_Init
flyingf4: handle returnvalue from PIOS_HMC5883_Init
quanton: handle returnvalue from PIOS_MS5611_Init
flyingf4: handle returnvalue from PIOS_MS5611_Init
quanton: moved PIOS_SENSORS_Init before uart inits
flyingf4: moved PIOS_SENSORS_Init before uarts init
pios_hmc5883: put value read and retriggering into one i2c transaction
flyingf4: use proper i2c adapter ids instead of MAIN / FLEXI port macros
flyingf4: add hmc5883 sensor orientation configuration
pios_hmc5883: correct bottom orientations
pios_hmc5883: added api to set sensor orientation
quanton, flyingf4: separated internal and external hmc5883 configs
flyingf4: made magnetometer optional