C-FOVE: Corrections

* GroundSubstitution: removed
* SimpleParfactor: correction to expand() method
* Tuple: correction in remove() method
* CountingFormula: almost completely rewritten
* ParameterizedRandomVariable: getRange() method and adaptations in
getMgu to process CountingFormulas correctly
* ParameterizedFactorTest: old tests rewritten
* SimpleParfactorTest and Pool: added one more test to check
unification with counting formulas
* Sandbox: new class for tests

Lots of corrections to make unification work without breaking the rest
of the code. The main change was made to CountingFormula, which now
can deal with non-binary parameterized random variables (that is,
PRVs f such that |range(f)| != 2).