Customizable Router Engraver

Engrave a design in a printable plaque with this Customizer. Design a plaque, draw a path to cut in it, and design a virtual [router bit](https://en.wikipedia.org/wiki/Router_%28woodworking%29#Available_cutters) to do the cutting. (The bit is designed by rotating a cross section, just like my [chalice lathe](http://www.thingiverse.com/thing:270289).)

**Lag Warning!**

This thing makes extensive use of the `hull()` command to compute the shape of the path cut between successive points. The T