LM8UU housing for Prusa i3 MK3

This is a remixed version that works on Prusa i3 MK3 bed carriage and probably also for the MK2 bed carriage.

**EDIT:** I personally really like these printed bushings from *@aeropic*: https://www.thingiverse.com/thing:2537701
Which need a housing to put them in. So I just changed the Anet housing that *aeropic* uses to fit on the prusa by moving the mounting holes to the correct location, changing their size to fit M3 screws and reducing the X/Y-Size as the closer holes make that possible.