Convert GTFS info to OSM format to help integrate them in OpenStreetMap

usage:

1) download and unzip a GTFS file into current folder

2) execute

    ./gtfs_to_osm.py

        -> generate an AGENCY.osm file

3) download all the stops in the wanted area, for instance with a request on https://overpass-turbo.eu/ :

        (
          node[public_transport=stop_position]({{bbox}});
          node[public_transport=platform]({{bbox}});
          node[highway=bus_stop]({{bbox}});
        );
        out meta;

4) save it in a file, for instace stops.osm

5) Add a line, for instance line 115 to the downloded stops.osm file:

    ./add-line.py stops.om 115

6) Edit stops.osm in JOSM and fix any generated TODO