Remove stops.zone_id
Add "alias" option to `model`
Speed up Route Directions generate

Switched to scanning already built "simplified stops" instead of
building off joins all the way down to `stop_times` table.

Also, updated `simplified_stops` to manually loop over [0,1] direction
ids, instead of `route_direction` objects, so `simplified_stops` and
`route_directions` don't have a circular dependency.
Fix execution order
Set html language to english
Support "to" stops for "/all_trips"