add option stopName arg to Stop __init__ for use in mareyPlot
hodgepodge update to gtfsDbManager to help with mareyPlot

Goal of these changes is to not affect any existing code that uses
gtfsDbManager.

in getStops, add optional arg stopIdList and sort output stops by
input order

in getUniqueStops, fix case where service_id is None

in getUniqueStops, fix handling of many trips using nested query
instead of long arg list

in getTripsDict, add serviceId to output dict

add getRouteIds, getServiceIdsForDay, getTripIdsForRouteIdServiceIds
methods which helped getting lists for testing, but didn't all end up
being necessary for mareyPlot
first version of mareyPlot shows GTFS schedule for one day/shape