Improved Radial Fan Holder

Additional radial fan holder for the customizable extruder:
https://www.thingiverse.com/thing:1383913

I had problems with mounting the Fan with just one screw, the screw guide of the fan broke out.
I also needed a distance block to reach my used end stop switch:
https://www.thingiverse.com/thing:1037870

So I decided to create a housing of the fan already includes the blower duct and the distance block for the end stop.