Use bio3d to generate illustrations of domain assignment in data pipeline

[AndrewRadev]

The snakemake pipeline could generate images that help us visualize domain assignment and normal modes using bio3d. The same script that does segmentation could also dump some images for demo purposes.

This tutorial under "Domain analysis with GeoStaS" does that: http://thegrantlab.org/bio3d_v2/tutorials/normal-mode-analysis. Some neat images from it:

AMSM visualization	Domain assignment with NMA

We should be able to do the same, although there will likely be differences in what functions we call. In the tutorial, they don't already have a trajectory and we do, so we'd have to look up the relevant functions in the documentation.