Printrcase external Printrboard enclosure with cooling

**I uploaded the wrong version of the body of the case, but it is fixed now.

I got tired of feeling how hot and steamy my printrboard was getting under the metal frame of my printrbot simple metal, so I designed a case to hold it outside the printer, and gave it a port for a 40mm cooling fan.

It allows for the wires to be tucked neatly away under the printer body while still getting the printrboard out from underneath. There are also zip-tie slots for keeping heat-bed wires, and the USB ca