migration script for the new resource field „registrationOpen“
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
Merge pull request #515 from leider/master

disabling registrability once an activity is full