Add GraphNotEmptyException class (need for RDF_loader)
Add enum WriteGraphType for RDF_loader.
Repair implementation and setting of RDF_loader.
Add WeiteGraphType to methods in RDFDataRepository interface.
Repair implementation of RDF_loader in classes Local/VirtuosoRDFRepo.
Repair tests using RDF_loader.
Merge branch 'master' of https://github.com/mff-uk/intlib.git