Allow and integrate documentation properties for ConceptScheme

[KlausIllmayer]

By definition the documentation properties (skos:note, skos:changeNote, skos:definition, skos:editorialNote, skos:example, skos:historyNote, skos:scopeNote) do not have a domain and range stated (see https://www.w3.org/TR/skos-reference/#notes - 7.5.1). Thus, they can also be used for a ConceptScheme and it may make sense for some of them, e.g. put general information about the vocabulary in skos:note. Currently, the ConceptScheme edit form does not have these documentation properties available, they are only available for Concepts. In my opinion, it would be good to add them also to the edit fom of ConceptScheme. Opinions?