enabled testing in pom.xml
refactured SparqlifyDump class (now SparqlifyDataset)

- renamed class SparqlifyDump to SparqlifyDataset because in the future
  it should also support a SPARQL endpoint served by Sparqlify
- subclassed Model
- modified iterator to yield Triple instances instead of Strings
  containing a dump line
- added readFromDump method
minor cleanup
extended metric initialization in measure data sink

- A metric now also provides its class when calling initMeasure on the
  measure data sink. This is mainly to be able to check which interfaces
  are implemented and which base classes exist
- updated all classes and interfaces involved in this change
- With this modification a BooleanTestingSink instance can now be used
  for testing triple and node metrics (dataset and mapping metrics are
  not implemented yet)
- used more specific method names in the BooleanTestingSink class since
  now more than testing of node metrics is supported ("written" -->
  "nodeMeasureWritten")
- added methods means to support testing triple metrics in
  BooleanTestingSink
- updated tests that use the BooleanTestingSink to the changes made
  there
added forgotten SparqlifyDataset.java file
introduced triple measure datum class (TripleMeasureDatum)
added differentiation between writing triple or node measures to sink

- renamed writeToSink method to writeNodeMeasureToSink
- introduced writeTripleMeasureToSink
- updated all places where the method is called, accordingly
extended dummy sink to log triple measures
implemented NoProlixFeatures metric

This metric checks if reification, containers or collections are used in
a given triple.
added tests for NoProlixFeatures metric