* [GV_ATTRS,FIX] Use the colorscheme/1 attribute for checking the color/1 attribute, if it is available.
* [GV_HASH,SC] Removed this module. Functionality was used by the IOTW project which now uses builtin predicates instead.
Started to rewrite the RDF(S) support modules.

* [RDF_GRAPH,SC] Reworking of this module.
** Relocated rdf_subgraph/2 from RDF_GRAPH_THEORY.
** Rewrote rdf_subgraph/2.
** Rewrote rdf_graph_instance/3.
** Rewrote the test for rdf_graph_instance/3 using plunit.
** Rewrote rdf_schema/4.
* [RDF_SEARCH,SC] Relocated rdf_beam/5 from RDF_GRAPH_THEORY.
* [RDF_SERIAL,SC] Relocated rdf_graph_source_file/2 and rdf_new_graph/2 from RDF_GRAPH.
* [RDF_TERM,SC] New module extracted from RDF_GRAPH.
** Added rdf_literal_equality/2.