Add phase and ordering respecting global statevector access

[GBoydQ]

Currently, statevector access from SeleneQuestStates must come from partial state access (necessarily throwing away global phase information by some convention) or the internal .state member

The recent fix of qubit ordering in state results #109 has revealed that .state can contain incorrect ordering information. Therefore, the simulator currently does not contain a way to get accurate statevector information without either throwing away ordering or phase information.

It would be useful to have a .get_global_state() that acts similarly to .state but keeping track of qubit ordering.