Merge branch 'master' of https://github.com/PX4/Firmware

src/modules/mavlink/mavlink_main.cpp

src/modules/mavlink/mavlink_messages.cpp

src/modules/navigator/mission.cpp

src/modules/navigator/mission.h

src/modules/sensors/sensors.cpp

src/platforms/qurt/px4_layer/main.cpp

...forms/ros/nodes/position_estimator/position_estimator.cpp

...atforms/ros/nodes/position_estimator/position_estimator.h