Add directed graph support

[Ameliorate]

In the KANI, directed graph support means that there are some rail lines that you can go in one direction, but not the other. This would help to simplify some TerminalDestinations like nyc and gabon by having one place to depart from, but many to arrive to.

Part of this would be asking if MoleBot can support this without significant modification.

[specificlanguage]

Just for record keeping, MoleBot already supports directed graphs as part of its implementation; just needs to happen at this point