Proposal - clarify agency_name, add agency_acronym and generic_service_name

[Jehiah Czebotar]

I'd like to propose this change to clarify some current usage, and
would like to hear specifically from some other data publishers and
consumers about this.

--
Jehiah

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Proposal Summary:

Clarify usage of agency.txt/agency_name to restrict acronyms
Add a agency.txt/agency_acronym field
Add a routes.txt/generic_service_name field

Motivation:

Managing and indexing larger sets of GTFS data becomes more difficult
because agencies use various ways of referring to themselves in the
agency_name field. Some use use the acronym version of the agency
name, some use the agency name, and some use a third branded service
name.

With different types of values in the current agency_name, this value
can't be used consistently, and makes consistency difficult across
various sources, and makes presentation of the common user facing name
of service difficult as that field value may or may not be what is
represented in agency.txt/agency_name.

Often it is preferred to represent service as "agency_name
(agency_acronym)" instead of just one or the other, and it might be
preferred to use generic_service_name as user facing navigation or
identification of name of service.

Proposal:

clarify usage of agency_name such that it must not be an acronym (ie:
all caps), and that it should be the name of the agency/company
providing transit service, not a branded name of the service.

add an agency_acronym field to agencies.txt which is optional and when
present is the acronym of an agency, and must be all caps

add a routes.txt/generic_service_name to routes.txt which is optional
and when present represents the proper term to refer to an aggregate
group of services. This will often be unique by dataset + route_type,
but that isn't a requirement (See examples).

generic_service_name should not be a generic word like "subway" or
"bus" unless it is explicitly a branded service name like "DC Metro".

Example 1:

In Washington DC Metro service is provided by "Washington Metropolitan
Area Transportation Administration" (also known as WMATA).

agency.txt/agency_name would be "Washington Metropolitan Area
Transportation Administration"
agency.txt/agency_acronym would be "WMATA"
routes.txt/generic_service_name would be "DC Metro" and "DC Metrobus"
as appropriate

Example 2:

in New Jersey Path train service into New York City is operated by the
Port Authority of New York and New Jersey.

agency.txt/agency_name would be "Port Authority of New York and New Jersey"
agency.txt/agency_acronym would be empty or not present
routes.txt/generic_service_name would be "Path"