Merge pull request #654 from NicoleRauch/master

Stripe now also gets a description (used for the payer's email notificat...
introduced explicit stripe total amount
Merge pull request #655 from leider/master

introduced explicit stripe total amount
test for marking payment received
small layout change - tables in payment overview pages non scrolling now
showing payment error to user instead of showing 500 page
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.