endstop holder for prusa

This is an endstop holder modified from the Prusa Mendel design. When we printed the old one out, the far hole was too close to the edge to render properly, for no particular design reason we could discern. We extended the end of this part by about 2mm and it prints a much better looking part, even with RepSnapper.

Also, this part is great for mounting TechZone's monotronics - use two.