Add route_patterns.txt, calendar_attributes.txt

[jfabi]

These changes will appear in the MBTA's GTFS on Thursday, January 17, 2019.

• calendar_attributes.txt (new file)
• route_patterns.txt (new file)
• route_pattern_id in trips.txt (new field)

Sample files encompassing all routes can be found at the following links: calendar_attributes.txt, route_patterns.txt, and trips.txt.

[jfabi]

The notes for route_pattern_name have been changed to reflect the fact that bus/subway names currently don't contain the origin.