Added some tests for activitiesCoreAPI.addVisitorTo. Also needed to add another parameter to the callback (because it is being invoked in so many spots).
Merge commit '8710770070ac030852373856f80c0f38804adbb7'
Merge pull request #514 from NicoleRauch/master

Nachlieferung: Ein paar Tests.
Merge commit '39245e260d4976bec56a497914e548b637cc211b'
migration script for the new resource field „registrationOpen“ - added deletion of color
disabling registratability once an activity is full