Fixes the bug of sending an e-mail notification only to the owner of the event. Also allows to send e-mail notifications to the members of groups that are shared with. Also checks that each recipient gets the e-mail only once, even if it belongs to several groups, for instance.
Fixed the fix to send e-mails to groups' users sharing an event.
Merge pull request #559 from quamenzullo/master

Fixes the bug of sending an e-mail notification only to the owner of the...