Cross-CiviCRM dedupe audit

We should do a cross-CivICRM search of places where we match contacts against dedupe results, and make sure that the matching is done in the following manner:

1. If there's exactly one match, the new data are used to edit the matched contact.
2. If there are no matches or more than one match, the new data are used to add a new contact.
3. If there's more than one match, decide whether there's somebody who should be notified about potential dupes in the database (like the event admin if the dupe check is done during registration for a given event).