Prusa felt X Axis for use with ACME lead screw and nuts

This is the rending of a patch that I have pushed to the prusa project which is still queued up for addition. It allows you to take your standard prusa X axis with LM8UU bearings and use acme 3/8" lead screw instead of the more usual but less smooth threaded rod.

Original sources can be found here:

https://github.com/prusajr/PrusaMendel/pull/26