Rename Agency AgencyRow, and create AgencyTable to store the AgencyRows.

It will be clear that the GTFS data as relational database structure.

The same thing as to be done for all the other GtfsObjects.
Rename CalendarDate CalendarDatesRow, and create a CalendarDatesTable to store the CalendarDatesRows.
Rename CalendarEntry CalendarRow, and create a CalendarTable to store the CalendarRows.
Rename FareAttributes FareAttributesRow, and create a FareAttributesTable
to store the FareAttributesRows.
Rename FareRulesDate FareRulesRow, and create a FareRulesTable to store the FareRulesRows.