[fix] removed old scim converter
[fix] throw exception if member not exists instead of silently ignoring
it
[fix] added null checks
[fix] replace() now uses dao.update for replacing a group
[fix] removed import of ScimConverter (it's gone)
[fix] removed findAndAddMembers(), this is now handled by converters
[fix] removed now superfluous fromScim() method
[test-fix] fixed tests to reflect recent changes