Only send publish notifications to users who can see results

Fixes #386.

Publish notifications are only sent
- if the course was published for everyone or
- if the user has comments about himself or
- if the user is responsible and there was at least one comment about one contributor or about the course.
yes, sure. they can't see anything so there is no need for a notification. the only possibility would be including a message: "the evaluation ended for these courses but nobody evaluated them: ..." would you like to have such a message?