K8200 improved Z-Axis holder

The least precise part of the K8200 seems to be the Z-Axis design.

There are a couple of good improvements, including using a flex coupling (just a few $) between the stepper motor and the rod.

This is a mod from thing:166023. I've used the original design before, however I needed to lower the whole axis to fit into the new coupling and the original design offered less space.

I've also replaced the Motor holder and the Z-Axis adjust. See my other designs/makes.