Messages interpreted in UAS.cc:
MAVLINK_MSG_ID_HEARTBEAT
MAVLINK_MSG_ID_SYS_STATUS
MAVLINK_MSG_ID_ATTITUDE
MAVLINK_MSG_ID_LOCAL_POSITION_NED_SYSTEM_GLOBAL_OFFSET
MAVLINK_MSG_ID_HIL_CONTROLS
MAVLINK_MSG_ID_VFR_HUD
MAVLINK_MSG_ID_LOCAL_POSITION_NED
MAVLINK_MSG_ID_GLOBAL_VISION_POSITION_ESTIMATE
MAVLINK_MSG_ID_GLOBAL_POSITION_INT
MAVLINK_MSG_ID_GPS_RAW_INT
MAVLINK_MSG_ID_GPS_STATUS
MAVLINK_MSG_ID_GPS_GLOBAL_ORIGIN
MAVLINK_MSG_ID_RC_CHANNELS_RAW
MAVLINK_MSG_ID_RC_CHANNELS_SCALED
MAVLINK_MSG_ID_PARAM_VALUE
MAVLINK_MSG_ID_COMMAND_ACK
MAVLINK_MSG_ID_MISSION_COUNT
MAVLINK_MSG_ID_MISSION_ITEM
MAVLINK_MSG_ID_MISSION_ACK
MAVLINK_MSG_ID_MISSION_REQUEST
MAVLINK_MSG_ID_MISSION_ITEM_REACHED (we want a new signal for this one)
currentWaypointChanged
MAVLINK_MSG_ID_MISSION_CURRENT
MAVLINK_MSG_ID_LOCAL_POSITION_SETPOINT
MAVLINK_MSG_ID_SET_LOCAL_POSITION_SETPOINT
MAVLINK_MSG_ID_STATUSTEXT
MAVLINK_MSG_ID_SERVO_OUTPUT_RAW
MAVLINK_MSG_ID_RAW_IMU
MAVLINK_MSG_ID_SCALED_IMU
MAVLINK_MSG_ID_NAV_CONTROLLER_OUTPUT
MAVLINK_MSG_ID_RAW_PRESSURE
MAVLINK_MSG_ID_SCALED_PRESSURE
MAVLINK_MSG_ID_OPTICAL_FLOW
MAVLINK_MSG_ID_DEBUG_VECT
MAVLINK_MSG_ID_DEBUG
MAVLINK_MSG_ID_NAMED_VALUE_FLOAT
MAVLINK_MSG_ID_NAMED_VALUE_INT
MAVLINK_MSG_ID_MANUAL_CONTROL
MAVLINK_MSG_ID_HIGHRES_IMU

Signals of interest:

On UAS.cc:
// General
value_changed (custom value tracking)

// Mode:
armingChanged (ARMED etc)
statusChanged
modechanged
navModeChanged

// System Status
loadChanged
Do we already have these in some form? Can they be merged?
batteryChanged
voltageChanged
gpsLocalizationChanged
satelliteCountChanged

// Mission status
currentWaypointChanged (on WaypointManager)
new type for MAVLINK_MSG_ID_MISSION_ITEM_REACHED
distToWaypointChanged

// Link Status
heartbeatTimeout
dropRateChanged

// Attitude & speed
attitudeChanged
speedChanged
speedChanged (when message is MAVLINK_MSG_ID_VFR_HUD: x is airspeed, y is zero and z is VV)

// Position (if used)
globalPositionChanged
homePositionChanged (for pointer to home. Or we ignore signals and suck the data
off the UAS instance)