Give MoMMIs a plasteel module

Since MoMMIs can't actually ask for plasteel, and have to nigger it from
Engineering, Robotics or EVA to the extreme distaste of anyone working
one, just give them the damn thing

The only use for plasteel, outside of building or repairing which is
exactly what MoMMIs should do, is building Mechs, so I can't see how
that could be massively abused