Subterps - Combinations of commentary for subparts, regtext, and appendices

This feature is not complete, but I wanted to provide it as a pull request to get it in as early as possible.

Changes:
* Adds views for partials and chrome around subterps
* Adds a function for determining which sections are associated with a subterp
* Fixes whole regulation viewing by adding variables for the view names/labels used by the versions tab
* Adds subterps to TOC results
* Modifies main toc template to include these results
* JS adjusts the link for diffs accordingly

Missing:
* JS doesn't highlight the subterp in the TOC
* No clean 404 page when it's a bad version (as the subterp is make-believe)
* Missing footer links in subterps