add param for qnh
sensors: move close to correct position
sensors: do not exit task on error
Reset excitement mode for hmc5883 sensor before applying a new one to avoid getting reserved 11 bits set in case of a set_excitement(1) call following a set_excitement(-1) call.
Merge pull request #1295 from muharred/master

HMC5883 set_excitement minor fix.
Merge pull request #1283 from PX4/qnh

add param for qnh
Merge branch 'master' of https://github.com/PX4/Firmware