C-FOVE: Counting and Unification

- ParameterizedFactor: Inclusion of auxiliary methods for Counting
- SimpleParfactor: inclusion of auxiliary methods for Counting and
unify() method
- Parfactor: methods for unification
- CountingFormula: methods for counting
- LogicalVariableNameGenerator: reset method
- ParameterizedRandomVariable: method to get empty instance
- Substitution: method to check if the set is empty
- SimpleParfactorTest: tests for counting
- Pool: method to create inconsistent constraints and thorough 
example for unification

Bugs corrected:
- range value is returning wrong values

Unification is still incomplete. Counting has been tested at some
level.