MK2s Y-belt holder

This is a remix of OCDs belt holder, that did not fit my version of the Prusa MK2s which is the later revision. It is basically his idea of the belt going straight trough the carriage holder applied on the original belt holder part from Prusa.

I also added a M3 and nut so it is possible to secure the belt tightly.

The gcode has 100 % infill.