STC-1000 easier print

The original was totally unprintable on my printer, largely due to the screw tabs floating in mid air and being printed with the right extruder then hit by the left one, but also the holes won't come out properly round if printed vertically.

So I cut a few layers off the bottom (only the feet) in PrusaSlicer and rotated the pieces so that they are flat on the build plate, also split the model in two so you don't have to.

It now needs some supports to print (see screenshots) but I have successfully printed both halves and it fits the STC-1000 perfectly.

Added a universal box generator remix too, not tested though and won't customize (needs openscad).