Created a rough test about detaching a task from a task-list.
Changed Hibenate-annotated private fields of domain objects from being a
List to being a Set. Expecting that some "cannot fetch multiple bags"
problem might be solved.
Fixed a bug in the *test code* - to save the modified domain object,
call `update`, not `save`, on the DAO! Cleaned the domain objects'
relationship-related implementations.