Add support for 0-based partition IDs

Initial goal is to allow user commands to specify partition IDs as short integers `[0, ring_size)` instead of hash values. May consolidate other features such as Yokozuna's logical partitions later.
I was attempting to make `edoc` treat that comment properly. It turns out I can move it to the line below the `-type` and `edoc` will still include it in the generated HTML.