Raspberry Pi 3 b case for mounting to v-slot

I needed a Pi 3b case that I could mount to the frame of my [D-Bot](https://www.thingiverse.com/thing:1001065). I found [WalterW's](https://www.thingiverse.com/thing:2078231), looked good, and added a V-Slot mount on the side. Top is unmodified from original and included only for completeness.

To keep things compact, the bottom of the case must be mounted to the frame *before* you install the Pi. I had to order screws, so getting M2.5x16 wasn't a big deal :). The mount requires M3x8s, which i