(No)Filament buffer for MMU2

My way to solve the MMU2 disaster.

First I took the mmu2 a litte bit steeper, to make sure that the sphere gets back, even if there is some dirt in the chamber.

Secondly I placed the spools above the printer on a simple construction. There is not really a need for the bearing, I just took them from the original spool holder.

Now the important things. **Reduce the friction !**
The PTFE tubes originally delivered by Prusa are far to long. I shortened them by the half.

keep everything smooth curved.

I never got more than 20 filament changes at a line.
Using the shown construction, the turtle was printed without any mmu2 fails