cubicweb-skos #6908096 add rdf views for Concept entity type [validation pending]

making it possible to export individual concepts, either in short or full form.

prioritynormal
typeenhancement
done in0.7.0
load left0.000
closed by#e921931093e4 Implement RDF adapters for Concept entity type
patchImplement RDF adapters for Concept entity type [applied]