Error to console when trying to set a state that doesn't exist.  Helps prevent subtle "WTF" bugs when a transition evaluates to true, but the state machine doesn't have the requested State.
Mostly working game combat state machine.
 - Start/BeginTurn/EndTurn/Victory/Defeat states are supported, with transitions to flow between them.
 - TODO: Currently you just attack back and forth forever until someone hits the spacebar.  Add some health/damage and make this do something real.