cubicweb-datacat #8494813 use controlled vocabularies for distribution format/media type [validation pending]

Use vocabularies recommended by DCAT-AP (See p. 28 of PDF specification) for Distribution dct:format and dcat:mediaType (same scheme apparently).

prioritynormal
typeenhancement
done in0.6.0
load1.000
load left0.000
closed by<not specified>
patchAdd and export `dct:format` and `dcat:mediaType` relations [applied]Export dcat:mediaType and dct:format for distributions [folded]