Enable Banning Domains

This feature already exists, admins can ban domains (and there are already banned domains). I can see how it might be a useful mod tool, but I think any domains banned at the moment are probably ones that deserve sitewide bans anyway. edit: To clarify, the domains we banned are all spam sites riddled with ads/trackers. Sometimes the domain is banned, but most of the time the user is banned after repeatedly posting spam links and not responding to attempts to contact them and ask them to stop.