Twisty vases via customizable polar graphs

This is a customizable wavy vase or cup. In the Customizer, you specify polar graph formulas for the bottom and top, as well as a formula for varying the diameter, and a twist angle, as well as the wall thickness and the bottom thickness.

The design may not work if your graphs have sharp cusps.

The OpenSCAD file uses (and bundles) my [tube mesh](https://www.thingiverse.com/thing:2406760) and [function parser](https://www.thingiverse.com/thing:2295309) libraries.

**Updates:**
* July 6-