Prusa i3 blower fan upgrade

### Update
19/11/2018: I have tested this upgrade and must say am very happy with the result. I modified the duct slightly to allow it to blow more directly on the printed surface. There is room for additional duct designs but right now its giving me beautiful prints with PLA.
18/11/2018: At this time I have not yet completely tested this design. I am waiting for some parts however have printed these and mounted on the printer and they seem functional. Let me know if you test it out.

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