Fixed property node type.
A property definition should return the property name when asked for it.
Make addMixin method work.
Extracted basic node creation.
Made getContainerURIFor method protected so that it can be used by subclasses.
getTypeOfPropertyOnNode method should now also work on regular nodes, not just JCRNodeWrappers.
QA-6105: createOrUpdate should properly return whether the operation was a creation or an update. Added associated test.