Update project information
Improve readability of bench modules
Clean up legacy unit tests

Test removed from test_bench_manager.py: it has been moved to sutils/decbench.py.
Removed unused import of uuid.

Test removed from test_benchable_store_virtuoso.py: there is not anymore a clear() method in BenchableGraph.
Fix postgresql (w/ sqlalchmy) unit test.

Make connection clearer in the unit test, user and password are now mandatory.

Add extra dependency: rdflib_sqlalchemy and psycopg2.