Altered clamp style X ends (SAE and kung fu grip)

I think the Aleph objects X ends are wonderful. That said I had to tweak a few things to make them work well for me.

I opted not to go with their version 1.1 as a basis because the original seems more than sturdy enough already, and is easier to make work with the larger #6 nuts and uses less plastic.

Changes:
nuts and bolts.scad values for M3 is changed to fit #6 nuts.

The clamp part has been altered to grip the smooth rod better - as originally posted, it just slid on my smooth rod.