Azteeg X5mini v1.1 mount for Kossel Mini 1515

Disclaimer: this mount is a serious pain to wire up. Inserting the stepper and smaller wires through the side holes is quite annoying. I'm going to try to split this into a clamshell and solve a couple of other problems.

I found a few issues in Atomsk's welcome refinement of the original.

I tweaked the scad file to resolve all through holes, fixed a dangling overhang and a few other small tweaks (including the fact that the play button on my boards seems to stick out further than expected)