X and Y-axis guides for MendelMax

Update: the X-axis would still occasionally skip. THE solution for that was to really tighten the belt.

The belts on my MendelMax tend to go sideways after some usage. If the belt touch the outer side of the pulley, sometimes it will skip a tooth and my print has failed.

The best option is off course to make the belt balance on the middle of the pulley, but then I have to make big replacement parts. Now I made a shortcut by putting 608zz bearings against one side of the belt. This is done