Remove unneeded import
Separate out PowersetStates from DFA

PowersetStates should handle most of state storage related work in DFA
In the process remove unused getState() method
Make AlphaElement template parameter
Remove unneeded variadic parameters

Variadic parameters was no a necessity,
same thing can be achieved by passing array.
This makes it more consistent, when NFAState is expected as paramter,
then array should be passed