Feature/306 em trigger lazy loading

[luxbe]

This PR fixes #306 by triggering lazy loading when EntityManagerImpl is presented with a LazyLoadingProxy in the contains and remove methods.

[luxbe]

The build fails because the following test DeleteOperationsRunner.removeTriggersLazyLoading fails only with the DeleteOperationsTest of the OWLApi implementation.

Executing the following statement:

((EntityManagerImpl) em).createNativeQuery("SELECT ?p WHERE {?s ?p ?o}", String.class).setParameter("s", entityA.getUri()).getResultList()

before and after the remove call within the removeTriggersLazyLoading test reveals, that before the remove call, there are 4 statments left from entityA:

0 = "http://www.w3.org/2002/07/owl#topDataProperty"
1 = "https://onto.fel.cvut.cz/ontologies/jopa/attributes#A-stringAttribute"
2 = "http://www.w3.org/2002/07/owl#topObjectProperty"
3 = "http://www.w3.org/2002/07/owl#topObjectProperty"

while after the remove call, there are still 2 statements left:

0 = "http://www.w3.org/2002/07/owl#topObjectProperty"
1 = "http://www.w3.org/2002/07/owl#topObjectProperty"

In the RDF4J and the Jena implementation, all statements are properly removed. Therefore, I believe that this is a bug in the OWL implementation.