Improved X idler and X motor mount for Aluminum Mendel

I didn't like the press-fit X rods (or drilled/tapped holes - not sure what was intended to secure them), so I added M3 trapped nuts to secure them. Also added another trap for second 8mm nut. Oh... and a couple spaces to reduce the amount of plastic.

[UPDATE] V2 has trapped nuts (M3 again) instead of drill dimples for the nut cap. I just tried drilling my first version and the lamination cracked (BOO wood screws!).