Improved Tantillus XY Ends

Remodelled to suit my build. The biggest problems I had with the original design were the clamp cracking through the thin section, and the printed bushes being very sloppy. The original design was passable, but it was made much worse by the poor print quality of my first set of parts.

- Bushing replaced by Xlube S48M 8 x 12 x 12 hatted bush http://www.mulfordengineering.com/pdfs/MEP-Finished_Products_brochure.pdf
- Takes an M4 captive nut
- Shape simplified and material added to strengthe