dc:title and dc:description of ontology become blank nodes

[pchampin]

in the generated JSON-LD, we have:

  "dc:title": {
    "en": "here the title"
   },
  "dc:description": {
    "en": "here the description"
   }

which assumes that dc:title and dc:description are declared with "@container": "@language" in the context, but they are note. As a result, when parsing the JSON-LD as RDF, the value of these properties become blank node without any property.