Renamed MAVLink message definitions to seaslug.xml.
The HIL node now detects the rudder properly and disables itself when the
rudder node is detected on the network. If an uncalibrated rudder node is
detected, it's also told to calibrate.
The primary controller now transmits only GLOBAL frame missions via
MAVLink. This allows the HSI and map to display them. The mission struct
was modified to enable this and now all missions are converted to
LOCAL_NED when stored internally and the old GPS lat/lon/alt are stored in
the new otherCoordinates struct member.

Additionally the GPS_ORIGIN message is transmit via MAVLink whenever a
MISSION_REQUEST_LIST message is received.