Nix expressions for CAMotics CNC simulation

I wanted to use CAMotics, which google tells me is the best open source gcode simulation program.

I wrote the nix expressions to get it working with the intention of a PR to nixpkgs, but the developer of CAMotics does some pretty non-standard things and I’m sure nixpkgs wouldn’t allow this. So instead I’ll just advertise my nix expressions here and hope anyone searching for the term CAMotics in NixOS will come across this.