TfL lookup better fallback to schedule

[AaronClaydon]

When the TfL lookup falls back from real-time to schedule it bases schedule look up on the last real-time journey arrival.

This doesn't work properly on stations near the end of a line as the last journey for one direction can be much later than the other (that's going towards the close end)

Should instead intelligently fallback based on platform or line/direction.