Add rights and copyrights to resource

[dennis-ruhe-npo]

Adds ec:hasRights and ec:hasCopyright to ec:Resource

We require ec:hasCopyright on our ec:Picture subjects. Adding them on ec:Resource seemed appropriate.

[JuergenGrupp]

Hi @dennis-ruhe-npo , thank you for your merge request. The Editorial Committee has discussed the issue and proposes a slightly different solution to your problem:

The class Picture will become a subclass of MediaResource. This allows Picture to link via instantiates to an EditorialObject and to Rights and Copyrights from there.

This retains to the principle that Rights are associated to EditorialObjects, no matter what physical representation as Resource it has.

The changes will be applied once the current restructuring of language packs is completed.
See #510