Radical

Implement JSON-LD writing for Jena :
    a no-brainer

￼Added some documentation for Generic Parameters, with @tparam :
    it is actually pasted in 3 files; maybe do that only in RDFStore.scala ?
As seen in  class RDFLanguages,
Jena offers only plain vanilla JSON-LD  , and rdf-json:
http://www.w3.org/TR/rdf-json

I remove here also extra package path .