* Fixed boolean SPARQL queries with a fixed rasqal lib.
* Implemented SPARQL boolean query support in Sesame2 backend.
* Improved removing of statements from default context in Sesame2 backend (no more listing and re-adding anymore

Does anyone know if it is possible to do "(Resource)null" in JNI?)

* Added convinience method to Model which allows to listStatements with Nodes instead of a Statement.
* Added new signals for removed and added statements to Model that actually have the statements in question as parameter. This is very important but I am not sure if using signals is too much of a slowdown.
* Enabled the boolean query test again now that both backend support it.