Add CIDR (network) notation support for rate limiter config

Whole networks can now be excluded from rate limiting using CIDR notation. Furthermore, the config has been adjusted to exclude all site-local networks from rate limiting by default.

This can be tested by looking at the response headers of API requests. The RateLimit-Remaining header will have the value infinite when the request originates from a site-local network. When the allowed networks are removed or changed to random public networks, the RateLimit-Remaining header will have a numeric value.

Closes: #205 (closed)
Depends-on: !672 (merged)