WOQL.delete_document unimplemented / documented

[GavinMendelGleason]

It's necessary to be able to delete documents in a woql query.

[spl]

Schema:

{ "@id" : "DeleteDocument",
  "@type" : "Class",
  "@documentation" : {
      "@comment" : "Delete a document from the graph.",
      "@properties" : { "identifier" : "An identifier specifying the documentation location to delete." }
  },
  "@key" : { "@type" : "ValueHash" },
  "@inherits" : "Query",
  "identifier" : "NodeValue" }