OO-3297, OO-3301: refactor security group management operations in its own DAO, implement isInOrganisation mfunction for course expert rules

OO-3297: refactor the user management to use organization for managing the roles instead of named security groups

OO-2947: Option to keep/delete user properties when Shibboleth delivers null and ensure that the mandatory user properties never deleted

OO-2891: Update the User only if some attribute values have changed. Wording, testing, mMinor improvements in code redability.

--HG--
branch : bps