Prusa Multimaterial upgrade heatsink PTFE cutting jig - 41mm

A very simple jig to enable precisely 41mm of 4mm OD PTFE tubing to be cut to insert into the top of the MMU heatsink. Insert tubing all the way into the hole and cut parallel and flush with the wall at the entrance point.

Please note that this is not the only step required with this tubing. It must also be reamed and chamfered (official specs [here](http://manual.prusa3d.com/Guide/How+to+trim+PTFE+tube+-+Multi+Material/497)). Also note that the inside diameter of this tubing is specifi