AC-FOVE: Split on X/t not involving extra logical variable

* AggregationParfactor: hashCode, equals, toString methods and split
structure
* And and Or: added hashCode and equals methods
* ParameterizedFactor: added applySusbstitution method
* Parfactor: removed unused, commented code
* Binding: added a contains() method
* Pool: corrections to structures to test split method
* BindingTest: test of contains()

First (and easiest) part of splitting aggregation parfactors is
implemented and tested briefly.