Interpolate edges of polygons

[jeffeb3]

When doing some of the latest changes, with pattern percentages, etc. It's clear that a 4 sides polygon is just 4 points. In the cases where it might matter, we should consider handling that a bit differently. If we just turned each side into dozens of line segments, that would work. That might also help with some of the other pattern manipulators, like the spinMath or growMath.

[bobnik]

Since this issue was added, we've added subsampling as needed in shapes and effects that benefit from the extra vertices. I'm loathe to auto-add them for performance reasons. Proposing we close this issue for now...