GTFS-RT ETA Accuracy Benchmark Stats

[evansiroky]

User story / feature request

As the transit data quality program,
I would like to have stats and measurements of the ETA Accuracy Benchmark,
So that I can analyze the quality of predictions at vendors,
and so that I can communicate to transit agencies about the accuracy of their current GTFS-RT feeds.

Acceptance Criteria

Prediction accuracies are able to be obtained for each stop in each stop_time_update and then aggregated potentially to each stop/trip/route/day.

Notes

This could eventually be a dashboard or could be put on the reports website.