Filament Guide and Improved Spool Holders for Original Prusa i3 MK2(S)

I had a few issues with the original spool holders:

- They were too short to properly hold eSun spools (the spool fell on one occasion).
- The absence of a filament guide means that sometimes the filament will get out of the spool and tangle.
- They have an excessively tight fit to the printer frame, mine broke 4 times, that I had to super glue it.

The idea of this design is to keep to the original idea, but solve this issues.