RepRapPro Ormerod X-carriage

Replacement X-carriage for RepRapPro Ormerod. It lacks the mount for the Z probe, as I am using dc42's replacement sensor (which mounts on the air duct). However, it adds two separate features to lock it in place on the X linear bearing, to keep it from sliding off during printing. A small hole for a set screw, and a groove to insert a piece of wire, that both line up with the groove in the bearing.

The STL file has a hole for M2 screws, can easily be adjusted for a M3 grub screw or something similar.
The groove is large enough to fit a thin electrical wire or MIG welding wire. Something with around 0.8-1mm diameter.

Based on [dc42's OpenSCAD remake](https://github.com/dc42/OrmerodSensorBoard/blob/master/OtherPrintedPartsForOrmerod/Xcarriage.scad) of the stock X carriage.