Reorganize/eliminate the tables/ and volumes/ output directories #37
Description
The tables/ output directory contains a hodge-podge of outputs. The contents of that directory don't directly correspond to any of the outputs in the config. Rather, they are copies of various the INPUT tables, emitted for debugging, etc.
At the very least, we should rename that directory. We should consider whether those exported files are necessary, and if so, whether it would make more sense to drop them into the flat/ output directory. It some cases, it might make sense to work them into the caching infrastructure (via the @cache decorator and related functions/classes).
There's a similar issue with the volumes directory. A better name would be roi-volumes. Even better, we should port the ROI volume stuff to the standard caching mechanism, too.