Update method addTriple in RDFDataUnitHelper interface, add method for creating URI,blank nodes, literals.
Remove method addTriple from RDFDataUnit interface, update method isTripleInRepository.
Update implementation in BaseRDFREpo via changes in RDFDataUnitHelper interface - close #348 issue.
Update calling method addTriple for testing in LocalRDFRepoTest.
Merge branch 'master' of git@github.com:mff-uk/intlib.git