improved handling of public attribute
Currently the public attribute (or E55_Type in RDF) is only present when an item is supposed to be public. Not all classes are publishable (public/non-public). When the attribute is absent it is not clear if the object is considered private or not publishable.
We should only consider some classes to be publishable. Objects of other classes are published if they are related to a public object (or always public).
publishable_types = {'person', 'text', 'witness', 'codex', 'collection', 'repository', 'place', 'subject'}
Edited by Robert Casties