integrate RDFUnit directly in the framework

[jimkont]

RDFUnit now has a JUnit integration where we can define a test RDF file and an ontology (NIF) and it can validate the input files through maven / IDEs etc.

the simplest approach is to create a new nlp2rdf-test module which as a build step generates sample result files from all other modules and stores them as resources (and replaces existing ones on every build). For each file we create a separate RDFUnit/JUnit test file that runs whenever we re-build

Later we can find more sophisticated ways to do it but this can be good for start, WDYT?