Updates to "exemplar" fields not applied to linked fields

[landonreed]

This issue was uncovered when a user reported that updates to the wheelchair_accessible field on routes were being silently dropped. For one, the field was not present in the Table definition. The second more critical issue discovered is that this "exemplar" field and fields on other tables (patterns and pattern stops) are not being applied to linked fields in referring tables. As a concrete example: the trips#wheelchair_accessible field is derived from the route#wheelchair_accessible field in the editor. Another example: pattern_stops has a number of fields (e.g., pickup_type and timepoint) that need to be applied to all stop_times that refer to trips on this pattern.

[landonreed]

We seem to be missing updates to Trip#shape_id field when Pattern#shape_id changes. Fix is inbound.