Prusa i3 MK2 Extruder - Easy hotend access

Note: Please check also the newer and more advanced design [Articulated part-fan](https://www.thingiverse.com/thing:2637257).


The Original Prusa i3 MK2 extruder is a very nice compact design.

However, to change the nozzle, one has to disassemble many of the extruder's parts, removing at least seven screws.

I've made a few changes to the original design, so the part fan and the fan nozzle are now a single unit. They can be easily detached by removing only two screws. The nozzle and the