Split ports into input/output

[mcmanning]

Split ports into input/output

[McManning]

Couple other thoughts in no particular order:

• If I were to split it out, I'd be able to create explicit InputPort and OutputPort classes - without worrying about Unity polymorphic list serialization headaches
• If I wanted to extend in the future into different port directions (e.g. Direction.Down, Direction.Up, Direction.ExecutionFlow or whatever actually makes sense for particular use cases), I'd have to make an explicit collection and methods per new direction. Whereas right now it's a simple AddPort(new Port(configured however I want)) and GetPort("Foo")
• While it's kinda awkward that IO can't have the same name, maybe that'd help reduce debugging confusion later?

[McManning]

For the storage format in runtime nodes, I'm going to keep this as a single list. Moving forward - I might look at changing the API to be more explicit, but since that won't be a breaking change on the format itself I'm moving this off the priority list for release.

[McManning]

Closing this out - I'm sticking with a single port list until it becomes a problem. At which point I can look at doing a 2.0 for it.