Moved a line in BjarkeGeobucket2 that is a boost to performance.
Moved PolyHashTable closer to BjarkeGeobucket2's hash table and removed several superfluous reducers.
Improved the implementation of ReducerHashPack so that it is a bit faster and so that it does not move monomials out of hash table nodes. The latter was a barrier to making changes in PolyHashTable.
Replaced the interface and implementation of PolyHashTable with the better hash table from BjarkeGeobucket2. That made BjarkeGeobucket2 superfluous, so it was removed.