simplification and fixes

[triffid]

hi.

thank you for the lovely redesign! I'm changing direction and going for prusa mendel now that I've found this!

When perusing the openscad models, I found them hard to read and understand, and the x-end-* nut traps had skins across their bottoms. I tidied up some of the files, made them significantly easier to read, removed some redundant transforms and rotations, and fixed the skins in the nut traps.

ps: editing openscad files in an external editor with familiar keys and syntax highlighting and pressing f4 in openscad is much easier than using openscad's own text editor :)

[nophead]

The skins in the nut traps are support material. Without them the circular hole above the nut would be printed in mid air.