cubicweb-jsonld #5269464 jsonld view for rsets [validation pending]

The jsonld view on rsets will look like the standard jsonexport view but will provide additional information so that clients be able to build richer UIs. For instance, a CWUser in a resultset will be transformed into something like:

   "@context": "",
   "login": "alice",
   "dc:title": "cwuser alice",
   // ...


The general structure should also expose some additional metadata such as rql varnames and therefore be similar to the standard sparql+json format.

done in0.1.0
load left0.000
closed by#47e614c2ae40 implement jsonld view for "any" rset (closes #5269464)
patchimplement jsonld view for "any" rset (closes #5269464) [applied]