Landing gear design: enable fuselage mounting

As discussed in https://git.rwth-aachen.de/unicado/rce-workflow/-/issues/9, wing_design and tank_design already enable a high-wing configuration. If I use this starting file (csmr-2020_startCSD.xml), the workflow breaks at the LG tool because no fuselage mounting option is implemented.

To increase the configurational options in UNICADO, this method could be implemented in the future.