#2 added some annotation to interfaces
#6 removed toString() from some variables, due to causing an errors, toString() is not able to evaluate since session is missing
#6 moved variables that describes versioned object to versioned type (PersistentVersionedObject)
#2 all BO will use ID of objects, objects itself are to be loaded inside BO and than passed to DAOs
#5 fixed tests to work on IDs of objects, which are passed to BOs