Thunderbird mail filter search term using mailing lists (and not whole addressbooks).

This addon was created because Thunderbird only allows filtering mail by whole Addressbooks, and not by mailing lists (bug 180013).

The addon creates new search terms Author from mailing list and Recipients from mailing list; these search terms only allow operators is in AB/is not in AB, and the dropdown on the right contains address books and mailing lists, too... Et voila, mailing-list-based filtering works!