K8200/3Drag Z-probe for Marlin Auto bed leveling

## What is this?
A rig to mount a small 9G RC servo, with an arm mounted Z-endstop, next to the extruder on a K8200/3Drag to enable the Auto bed leveling feature in recent [Marlin](https://github.com/ErikZalm/Marlin).

I had to modify the [probe holder](http://www.thingiverse.com/thing:167430) by [zenmaster](http://www.thingiverse.com/zennmaster) a bit to account for my servo horn being a tad to wide and chisel shaped, not fitting in the original design.

My fork of Marlin with K8200 speci