Bowden extruder mount for RigidBot

This mounts the standard RigidBot extruder to the 20mm bars, and has a threaded hole that fits a 1/8" BSPT bowden coupling (10mm threads). This is the coupling that came with the Bowden version of the E3D v6 hot-end.

I included the DesignSpark Mechanical drawing for your remixing pleasure. DesignSpark Mechanical is astonishingly good, and happens to be free BTW.

Note that the pictures represent a v1 (beta) that I didn't release, so you'll notice some minor enhancements.