AC-FOVE: Generalized Aggregation Parfactor Multiplication

* AggregationParfactor: must be aware of
GeneralizedAggregationParfactor to do multiplications
* GeneralizedAggregationParfactor: multiplication method
* SimpleParfactor: must be aware of GenerazelidAggregationParfactor to
do multiplications
* GeneralizedAggregationParfactorTest: correction on multiplication
test