Api doc categories

[Marcus Sorensen]

I've spent a few minutes trying to figure out how API commands are linked
with their categories in the API documentation. I read the doc about
annotations and generating the docs. I see the known_categories in
gen_toc.py, but I don't see any place in the annotations where one might
define a specific command under a specific category. When I build I do see
it complain about uncategorized commands, such as the ones in the netapp
plugin (or whatever provides the 'filer' commands).