Marauder mech parts can't be constructed properly

Created by: JustSumBody

The designs don't show up even if you are at max research, from what I'm seeing they're supposed to show up under the Durand category. In addition, the build_path for the chassis still points to the durand's chassis. Even if they could be printed, attempting to print off the marauder chassis would have probably printed a durand instead. Their id is also still set as "durand_chassis" and "durand_larm" etc, not sure if that will cause other problems. @JMWTurner