cubicweb-dataio #3774875 Add vocabularies in XY [validation pending]

Add a function to XY to add vocabularies. These vocabularies will be used in relations creation (instead of using ExternalUri).

prioritynormal
typebug
done in0.5.0
load0.200
load left0.000
closed by#ec1ceaa9c580 [xy] Add a function to XY to add vocabularies, closes #3774875
patch[xy] Add a function to XY to add vocabularies, closes #3774875 [applied]