Storybook tidy-up

[mkhorton]

Mostly in a good state, the table of contents for the storybook might make more sense after the re-organization in #217

This is not worth spending too much time relative to other tasks since it's mostly for prototyping and demos, but there are still a few things we could improve, for example:

• Using realistic data for periodic table heat-map
• Using realistic data for the 3D crystal viewer demos, especially for animation and bezier demos