Added config option to switch off email notifications.

dav_events/emails.py

@@ -49,6 +49,8 @@ class AbstractMail(object):
         raise NotImplementedError()
 
     def send(self):
+        if not config.ENABLE_EMAIL_NOTIFICATIONS:
+            return None
         subject = self._get_subject()
         body = self._get_body()
         sender = self._sender