OO-1644: add managed and externalId to calendar events, add configuration for managed calendars at the same place as groups and courses, block edition of managed events

OO-1647: remove auto-subscribe of course calendar, list of course which the user is member of and which have a calendar ( as configuration or as course element)

OO-1654: fix the workflow editor of group tasks blocked by the select box of invisible relative dates

OO-1653: fix NPE if the identity is not found, replace the user name with the full name of the author

OO-1640: update the reference checkbox if the user need to choose between several types of resources