Sending confirmation emails on payment confirmation
Merge pull request #657 from leider/master

showing payment error to user instead of showing 500 page
Now the participant page also shows how many spots are available in a resource.
Merge pull request #658 from NicoleRauch/master

Now the participant page also shows how many spots are available in a re...
Merge commit 'cd6b81d753fa28781ca6fc651b9b293614a05b29'
sending mails re-done