Merge pull request #4810 from DonLakeFlyer/SpecifiesAltitudeOnly

src/FirmwarePlugin/APM/MavCmdInfoFixedWing.json

src/FirmwarePlugin/APM/MavCmdInfoMultiRotor.json

src/FirmwarePlugin/PX4/MavCmdInfoFixedWing.json

src/MissionManager/FixedWingLandingComplexItem.h

src/MissionManager/MavCmdInfoCommon.json

src/MissionManager/MissionSettingsComplexItem.h

src/MissionManager/SimpleMissionItem.cc

src/MissionManager/SimpleMissionItem.h

src/MissionManager/SurveyMissionItem.h

src/MissionManager/VisualMissionItem.h