Feature/ratio suburb lines

I think this one probably doesn't make sense to calculate on a per-route basis; it's a ratio of the number of routes that have suburban stops, so you need at least two routes to calculate it. At the moment though, we don't have a way to specify that an indicator doesn't have a certain type of calculation, so this should probably be:
`def calcByRoute(period: SamplePeriod): Map[String, Double] = Map("notImplemented" -> 0.0)` or something similar.