* Cleaned the code for not used variables
* added rete function towards rete_network implementation, which
constructs a list of pairs of (AM, BM)
* Added new type, rete_dataflow and refactored the rete function and the
9'' test to use it.
* Fix a bug in the join function, which failed when multiple solutions
were associated with the same Variable
* Added new functions towards the standing query implementation which
includes definig new type for the Rete network data flow (needs more
tests)
* Renamed tests to fit the OUnit convention 
* Test 8, slightly changed, to include extra tuples