Replace query:include with SHACL

[tpluscode]

Currently the use of query:include requires that additional assertions are made about a class, which is likely a term from an external vocabulary. For example to load friends when a foaf:Person resource is loaded

foaf:Person 
  a hydra:Class ;             # this changes the semantics of external resource
  hydra:apiDocumentation <> ; # this is necessary to be picked up by ApiDocumentation loader
  query:include 
    [ query:path foaf:knows ] ,
    [ query:path foaf:account ] ;
.

Instead, it would be beneficial to create an independent shape resource (subclass of sh:Shape) which would use SHACL's targets and semantics for defining how to load representations. Later SHACL Advanced Features could also be added.

</api/Peron#representationShape>
  a hex:RepresentationShape ; # rdfs:subClassOf sh:Shape
  sh:targetClass foaf:Person ;
  sh:property
   [ sh:path foaf:knows ] ,
   [ sh:path foaf:account ] .

This should be incorporated into the load query but possibly could remain a separate DESCRIBE as it is now implemented

DESCRIBE ?this ?include {
  ?this a foaf:Person .

  {
    ?this foaf:knows ?include
  }
  UNION
  {
    ?this foaf:account ?include
  }
}
VALUES ?this { <...> }