consolidate "collection_id" and "map_id"

[Jeffrey Warren]

map_id seems unused and could be swapped:

    MapKnitterExporter.run_export(
	      id, # sources from first image
	      scale,
	      export,
	      map_id,
	      ".",
	      @data,
	      key
    )

We'd need to update the sinatra app downstream as well.