Commit in haste: Repent at leisure. Fix reverse journey

Had not actually tried out my changes, or, it seems, used my brain at all
in making them.

- Can't simply just add Pi on, need to keep it within 2*Pi limit
- Also forgot to get compass direction
Bug fix - Forgetting than list indexes start at 1

Which means I also need to wrap around the list if I get 16 segments.
I.e. both 0 rads and 2*Pi rads are valid.

This means I probably could have just simply added Pi (previous commit)
to reverse the journey as I can just keep wrapping around. Oh well.