New Z Stop Screw Holder for D-Bot

The screw holder for the Z-Stop Set Screw on my D-Bot was moving too easily. This is a re-mix of the original with M5 threads and an insert in the bottom to for an M5 nut.

I've also included the STL for an M5x0.8 index ring that you can use on the nut to make 0.1mm Z height adjustments.