reorganized docs to add subcategories

[chughes-lincoln]

Mainly reorganized the docs to add a few subcategories to make things easier to find (i.e. all the searches are together rather than trying to find them in an alphabetical list).

Also added a doc showing how to change the default location format. I also had to add :titlesonly: to the main index, or else all the other categories would expand as well, rather than just the how-to subcategories (I haven't worked with rst/Sphinx before so maybe there are other/better ways of doing it, but it seemed to work well).