small clean-up
moved old DAG and small changes to TBoxReasoner
small fix to the test
better support for top and bottom properties
better support for owl:Thing and owl:Nothing
test for OWL 2 QL compliance extended
comments in OWLAPITranslation and minor adjustments for datatypes
cleaning datatype predicates
small changes to datatypes
eliminated two switches
datatype refactoring
replacing switches
two more switches gone
isolated a large chunk of datatypes
moved code from SQLGenerator to TypeMapper
small changes to TypeMapper
Merge branch 'develop' into feature/tboxreasoner-improved

Conflicts:
	obdalib-core/src/main/java/it/unibz/krdb/obda/model/impl/OBDADataFactoryImpl.java
	obdalib-r2rml/src/main/java/it/unibz/krdb/obda/r2rml/R2RMLParser.java
Merge branch 'feature/tboxreasoner-improved' of github.com:ontop/ontop into feature/tboxreasoner-improved
small changes to remove the ugly bit in SparqlAlgebraToDatalogTranslator
cleaned DatatypeFactory a bit