Add configurability for hardcoded values

[shazow]

A lot of these default hardcoded values make sense for public servers but don't make as much sense for private servers. We need to make them configurable.

• IO rate limiting
• Message rate limiting

... What else are we forgetting?

[ghost]

I would suggest that a --noratelimit flag (or similar) would suffice initially for a private environment. At least that would serve me. ;o)