Improve plotting utilities #23
Description
In particular,
- build functions around sequences of point render sets (sequence of sequences of sets to be rendered with distinct styles)
- experiment with 3D plotting and 3D plot animation (can unroll steps or distinct sets into 3rd dimension)
- add helper functions for multi-chart plots that work both for grid PNGs as well as animated sequences (take a single drawing area plotting function and call it with different backends)