Add ability to filter out specific hostnames when counting paid views/clicks

[ericholscher]

I had a user mention that we should probably filter out localhost on our side when counting paid ads & clicks. This is tricky because some of our publishers pageviews actually come through with localhost on their referrer because of a configuration issue on their hosting. We probably need to have a publisher-level ability to either opt in or opt out various bans, but it's definitely something we should consider as a feature.

[davidfischer]

Localhost should probably be filtered out always and it can be by blocklisting referrers however that's site wide and not publisher specific.