[Bug 785850] Limit votes on answers and questions

Limit votes on answers and questions to 10 votes per day of either type. Votes after the limit of 10 will be silently ignored. The limit is based on IP addresses for unauthenticated users, or user id for authenticated users. Authenticated users are not limited by IP at all.

The tests are kind of complicated, but they work. The alternative is somehow trying to make the rate limits different during tests, which I'm not really excited about.

r?