Merge branch 'attributescloneable' into develop
This branch makes attributes being Cloneable. For attributes, the default shallow clone implementation is used. This is good as long as attributes do not have mutable sub-objects. Note that VShape objects are not and must not be mutable. ScenarioElements implement a clone method. Implementations use a constructor and pass cloned attributes. ScenarioElements are not Cloneable because they do not user super.clone() which makes a shallow copy.