Should pictures go in folders with text?

Almost all pictures are currently in `_static`. They should probably be in the subfolders with the relevant documents for nicer organization leaving only heavily re-used pictures in `_static`

Start by reviewing the images in _static and the training documents that reference them. Move document-specific pictures into the relevant subfolders, retain heavily reused pictures in _static, and verify that image references and rendered training material still work.

Written by the indexing model from the issue text.