The fourth commit in the process of updating all graph theory code.
The initial phase of the process is now considered to be complete.
There are several pending integration tasks left, but these will be performed when they become relevant to a project or when I have some spare time.
Important thing to note is that WebQR works for the most part now, as far as the graph theory code is concerned. Now there will be some testing and more granual improving of the changes committen over the last three days.

* [DCG_GENERIC,EXT] It is not so easy to use meta-predicates in combination with DCGs... Rewrote dcg_multi_list//2 to make this somewhat work.
* [CODES_EXT,EXT] put_codes/2 can now write to any output that works for with_output_to/2 (this used to be only streams).
* [DGRAPH_EXT,SC] Updates this module to no longer cause conflicts with the other graph theory modules. This module has to be cleaned up later.
* [EXPORT_GRAPH_HTML,SC] Simplified the main predicate (no options argument anymore).
* [GRAPH_EXPORT,NEW] Now that this module is almost entirely removed, we start adding new predicate to it, that work in the new graph export context.
* [GRAPH_EXPORT_GRAPHVIZ,FIX] Many fixes and general improvements to the new DCG code.
* [GRAPH_EXPORT_SVG,FIX] Various fixes.
* [GRAPH_GENERIC,SC] Relocated the predicates from the old UGRAPH_BETWEENNESS module. We will integrate them with the other GRAPH_GENERIC predicates in the future.
* [GRAPH_GENERIC,SC] Relocates beam/6 to RDF_GRAPH_THEORY (RDF specific predicate).
* [GRAPH_WEB,FIX] Several fixes. This should be updated to work with GRAPH_GENERIC in the future.
* [PRINT_EXT,FIX] Several fixes to print_collection/2.
* [PRINT_EXT,SC] Removed print_list/3 and print_set/3 (no more indents).
* [RANDON_VERTEX_COORDINATES,SC] New module containing the predicates for generating random vertex coordinates.
* [RDF_EXPORT,NEW] Finalized the methods for exporting an RDF graph to GIF. Quite some work...
* [RDF_GRAPH,NEW] Added rdf_term_name/2, wrapper around rdf_term_name/3.
* [RDF_GRAPH_THEORY,NEW] Added rdf_edges_to_vertices/2 and rdf_neigbors/3.
* [SKOS_READ,FIX] Various fixes.
* [SPRING_EMBEDDING,FIX] Several fixes. This should be updated to work with GRAPH_GENERIC in the future.
* [UGRAPH_EXPORT,SC] Various small improvements.
* [UGRAPH_WEB,FIX] Various fixes. This should be merged with GRAPH_WEB.