OO-2057: adapt the course element for the new binder, the assessment tool to view the details of the new binder and the binder resource

enable floating entries with ownership

OO-2052: remove group memberships first to prevent timing issue with the asynchronous removing of subscription (patch S. Clemenz)

OO-2057: add more panels in home with dummy contents, add file storage, add poster for binder and page...