Added SPARQL public predicate and updated gitignore.
Started adding support for the BAG dataset.

* [BAG,NEW] New module accessing the BAG dataset.
* [DBPEDIA,FIX] Rewrote the WHERE-clause of the find_dbpedia_agent/4 predicate, adepting to the improvements made to formulate_sparql/5.
* [DC,RDF_NAMESPACE,SC] Renamed namespace 'dcterms' to 'dc'.
* [RDF_NAMESPACE,EXT] Added namespaces for bag, bags, ogc, plod, prv.
* [FILE_EXT,NEW] Added stream_to_file/2.
* [SPARQL_EXT,FIX] Made the port number optional in opening an HTTP connection to a SPARQL service.
* [ATOM_EXT,EXT] Extended predicates for stripping atoms, adding an argument for the charcters that are to be stripped.
* [GRAPHVIZ,OS_EXT,SC] Use process_create/3 instead of shell/2.
* [OS_EXT,SC] Removed the unused predicate run_shell/1 (we now use swipl library process instead).
small
* [FILE_EXT,FIX] file_name/4 used to give the file type, now it gives the file extension.
[ATOM_EXT,NEW] Added codes_repalce/4
Finished codes_repalce/4
merge
Merge branch 'master' of https://github.com/wouterbeek/STCN
* [KMC,EXT] Added KMC-annotations and references to the KB webste to STCN properties.
* [SC] Removed modules that are already in the PGC.