Fixed: (please cherry-pick)

Fixed: (please cherry-pick)
- em.remove() needs a managed entity, not a one passed from e.g. a controller
- still this method may throw an exception, e.g. when an other entity (table) references this entity
- but since deleteCellphoneNumber() *should* delete cell phone numbers, it doesn't care if the entity is still referenced.
- this needs to be taken care of the controller and not the EJB (job-executor)