fix issue https://github.com/mysema/rdfbean/issues/56

Loading RDF-files to Virtuoso is accomplished by parsing
the triples from the input stream using a Rio-parser.

A custom RDFHandler will take care to push the extracted
statements in batches of 5000 to the repository. This approach
should support even very large RDF-files.
Merge pull request #57 from pepperbob/master

fix issue https://github.com/mysema/rdfbean/issues/56