proposal: add agency_phone field to agency.txt

[Joe Hughes]

Summary:
Add an "agency_phone" field to agency.txt to specify the telephone
numbers for agencies.

Motivation:
The GTFS currently has "pickup_type" and "drop_off_type" fields in
stop_times.txt, which allow a stop to be specified as "Must phone
agency to arrange pickup/dropoff". However, without a telephone
number, it's difficult to present this information to the rider in a
useful way.

Proposal:
The following field would be added to agency.txt:
---------------------------------------------
agency_phone (optional):
This field, if present, specifies a single voice telephone number for
the given transit agency/operator. This field is a string value that
presents the telephone number in a manner consistent with the customs
of the agency's service area. It can and should contain punctuation
marks to group the digits of the number, but it should not contain any
other descriptive text.
---------------------------------------------

Example:
agency_id,agency_name,agency_url,agency_timezone,agency_phone
BART,Bay Area Rapid Transit,http://www.bart.gov,America/Los_Angeles,415 465-2278

Discussion:
I chose BART as an example because they make their feed freely
available, but it's a salient example because BART has several contact
telephone numbers with different area codes. Do we need to have a
more complicated means of specifying phone numbers to account for this
type of situation?

Joe Hughes
Google Transit