Allow IPs to be whitelisted

[pkevan]

Currently we utilise https://github.com/WordPress/wordcamp.org/blob/production/public_html/wp-content/mu-plugins/utilities/class-form-spam-prevention.php for ticket and other form submissions - most of the time this works fine, but on occasion it would be nice to be able to whitelist an IP, probably for a period of time, similar to how other whitelisting works on the wp.org network.