Prusa i3 - Spool Holder

Just another Spool holder for the Prusa i3 Mk2.

The one included by default was not working well for me. I tried to design this so that the conical surfaces fit as many roll diameters as possible while reducing the friction between the roll and the holder (not it is just the edge of the spool what touches the holder.

I added a small wedge so that the holder snaps into place and remains there. This also allows for the part to not be super tight, meaning that it is easier to move around to s