blocks table: add is_interline and dwell_time columns

[fpurcell]

is_interline = trip_id's end_stop_id === next_trip_id's begin_stop_id

dwell_time = next_trip_id's stop_time at its begin_stop_id - trip_id's stop_time at its end_stop_id
(e.g., begin_stop_id === end_stop_id ala is_interline shown above)