Dial gauge for the Moai Z axis

This is a dial that can be placed on the top of the Z axis threaded rod to indicate bed movement. This is useful for debug of skipped layers, etc, as well as confirming the layer height. On my printer, there wasn't enough rod extending past the build plate in the fully retracted position for the dial to screw on fully so I ended up gluing it in place after screwing it as far as it could go.