50mm print fan / blower guard for Prusa i3

Now on v2. New for version 2:

* in some cases the original bolts weren't long enough with the guard added. The thickness under the bolt has been reduced
* bottom edge has straight cutout so that the guard doesn't touch the duct for the print fan
* bolt heads sit flush for a cleaner look
* the surface in the STL is solid - can hack the slicer to make the mesh. This gives faster prints, uses less material, and better airflow since the mesh lines are all a single line of material.

To print