AC-FOVE: Generalized Aggregation Parfactors

* AggregationParfactor: sum out method
* Operator, Or and And: apply operator to 3 arguments
* Parfactor: no changes, only reorganization of methods
* CountingFormula: Histogram is now public, with one method available
* AggregationParfactorTest: test for sum out
* Pool: data structures for new tests
* GeneralizedAggregationParfactorTest: set of tests for generalized
aggregation parfactors
* GeneralizedAggreagationParfactor: skeleton of generalized
aggregation parfactor

Sum out for aggregation parfactors that I forgot to commit...
Setup of tests for generalized aggregation parfactors.