Show stop_code rather than stop_id on schedule

[CharlesBelov]

GTFS defines stop_id as internal and stop_code as public-facing. Therefore, I would expect the schedule, both HTML and PDF versions, to show the stop_code rather than stop_id.

[fpurcell]

You're correct...added to the todo list.

(FWIW, when TTPUB's gtfs loader was built, stop_code wasn't part of the gtfs spec...not sure there was really even a spec at that point).