Anonymous User Rate Limiting

[Bekabyx]

Given this project is intended to be open to the world, rate limiting is essential to protect this projects resources.

Exact limits are something that will evolve over time as expected traffic becomes clear, but the groundwork has to go in sooner rather than later.

This limit will probably have to be AnonRateThrottle for now, but if/when user authentication is required a higher limit may be considered for authenticated users. That's a separate issue for another time.