hmc5883: properly reset mag to normal state on calibration fail

and add current output in "hmc5883 info"
tone_alarm: Added arming failure tone
Merge pull request #801 from PX4/hmc_fix

hmc5883: properly reset mag to normal state on calibration fail
Merge pull request #802 from PX4/arming_fail_tune

tone_alarm: Added arming failure tone
sf0x driver: Stop emitting error messages once there is no hope this sensor will recover - continue to output error messages if the errors are just intermittent
Merge branch 'airspeed_scaling' of github.com:PX4/Firmware into testtest
Merge pull request #804 from PX4/laser_error_management

sf0x driver: Stop emitting error messages once there is no hope this sen...
Merge branch 'master' of github.com:PX4/Firmware into system_power