Specifications for editor component return value

[jsheunis]

Editor components should be in charge of returning value to the formData structure that is both valid (based on any/all fields of the property shape) and correctly formatted (based on the property shape's nodeKind and datatype fields), taking into account that the shacl-vue applicaton will handle this value together with its property shape when adding it as a quad to a graph store.

E.g. for a URL field that has datatype XSD.anyURI, the editor component should be sure to return a string (i.e. literal) that has the correct formatting, but not as RDF. So the shacl-vue application will create:

rdf.literal(String(editor-component-value), XSD.anyURI)