Remove unique index on person attributes.

People should be scoped to different accounts.
Models to determine nicknames for people and summaries of convs.

These are obvious places for more work to be done later :)
Cleanup routes.
Conversation view implemented.

This is a massive commit, please do as I say, not as I do. It breaks a lot of existing functionality which I'm going to add back in ASAP. In particular:

* The homepage has changed.
* Some of he form styles are broken (but we're not actually using them anywhere)
* Keyboard shortcuts don't work
* Replying to messages doesn't work
* Search doesn't work

I think most of those are pretty trivial to add back in. However, this commit was out of time pressure, not because it's a great example of how we should work. Please bear that in mind.