Major Description
Current method to make a packed FST:
1. Create an FST Builder with willPack=true, telling it you are later going to pack() it.
2. Create your fst with finish() as normal.
3. Take that fst, and call pack() on it to get another FST.
This makes no sense. if you pass willPack=true, then I think finish() should just return a packed fst.