* [RDF_META,EXT] Rewrite of meta-calls on RDF files. It is now possible to have a directory or a list of file as input (used to be only a single file).
* [RDF_SERIAL,SC] Rewrite of rdf_load/3 and rdf_save/3.
* [RDF_SERIAL,SC] Removed rdf_load_into_one_graph/3; use RDF_META instead.
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