Completing the refactor

In early January, it became clear that the class heirachy

Homomorphism -> Automorphism
Automorphism -> PeriodicFactor
Automorphism -> InfiniteFactor

was making it difficult to implement the Power Conjugacy problem. (The symbol '->' stands for 'is a superclass of'.) The solution was a different heirachy

Homomorphism -> Automorphism
Automorphism -> MixedAut
Automorphism  ->PeriodicAut
Automorphism -> InfiniteAut

where the type of an automorphism was determined at creation time by computing the quasinormal basis. This refactoring was a pain but was worth it.