Merge pull request #158 from Open-MBEE/master

Vocabulary for OWL2 RDF-based semantics
#160 Don't use Jena's RDFDataMgr.write(...) because it
effectively attempts to write the graph as if its base URI were null. 
For lang == Lang.RDFXML, this will cause a BadURIException if the graph
contains a Resource with a null URI.
#160 - verify that the graph read/write operations succeed
#156 - switch to the non-deprecated read API
#156 switch to the non-deprecated read API