/// <summary>
/// Opens a new state. Opening procedure is finished by calling SetTransitionInFinished.
/// </summary>
/// <param name="state">State to be opened.</param>
protected virtual void StartState(IAppState state)
{
_currentState = state;
_currentState.EnterFinishedSignal.AddOnce(EnterFinishedHandler);
_currentState.ExitFinishedSignal.AddOnce(ExitFinishedHandler);
_currentTransition = TransitionType.Enter;
state.PerformEnter();
}