add admin mail notifications

[sibalzer]

Another feature that I would like to see, is a notification mail in case there is an IP ban. There should be an option to send this mail to a different set of addresses to avoid spamming the group.

Originally posted by @DennisWilken in #5 (comment)

[paulypeter]

I think this should be a separate section in config.ini as well, as it should be different from the regular notifiers.
Maybe in a new section [ADMIN]