This is a trial for making the xy cable housings switchable, so that a
main_body can be built without any cable housings. The z cable housings were already made switchable for the Upright version. This will be neater when motors are not used. The current version of the thumbwheels are not mentioned in the instructions and bind on the cable housings #265.
Short stubs of the cable housings are still needed to join the mounting lugs to the body and provide a home for the logo and version number.
This will wait for v7.0.1