Additional state options needed for RungeKuttaPhase and solved pseudospectral phases

[robfalck]

Options fixed_initial and fixed_final are not sufficient to determine the direction of integration of each variable. Change the current state option direction (used only by RungeKuttaPhase at the moment) to time_direction.

Options connected_initial and connected_final specify that either the initial state value or final state value is to be connected to another output.

If options fixed_initial or fixed_final are True, then the optimizer owns those values and the initial/final values are not design variables. If they are fixed then they cannot be connected. fixed_final cannot be used in forward shooting (time_direction = 1) and option fixed_initial cannot be used with backward shooting time_direction = -1

If options fixed_initial or fixed_final are False, and the respective connect_initial or connect_final is False, then the initial/final value is governed by the optimizer as a design variable.

There are various combinations of these options that are invalid that need to be checked.