Add new methods to check if such modifier exists or not.
Add new method interface to check if the predicate uses "triple" symbol.
Add immediately known prefixes in the SimplePrefixManager class.

This implementation removes the need of users to add known prefixes in
their code (including in the test cases).
Add hasModifiers() method interface to check if the query has modifiers.
Add new vocabulary for Quest query predicate "ans1".
Update the string representation for Constant objects.
Initial implementation of Datalog-to-SPARQL translator.
Make the test cases for the Datalog-to-SPARQL translator.
Introduce new package obdalib-sesame containing all transformations
between Sesame and Quest API, and R2RML manipulation
obdalib-sesame changes
new files obdalib-sesame after git index
Create first version Datalog to SPARQL translator
Create test cases for DatalogToSparqlTranslator
Integrate the DatalogToSparqlTranslator with Quest.
Fix quotes in preprocess SQL query in Quest
new test case for r2rml join nodes testing
Add getSPARQLRewriting() method interface for user service.
Add method to check if a function is a class or property.
Use the colon instead of empty string as default prefix.

Jena API uses empty string "" instead of colon ":" as default prefix.
The adaptation is required because Ontop prefix manager requires colon
as default prefix.
Add new test case to use Quest for doing Datalog to SPARQL service.