Support custom router URL for OpenTripPlanner
Some OpenTripPlanner instances put the REST interfaces for the router interfaces behind a fixed URL, so that /routers/default is not available. Such as TriMet with https://maps.trimet.org/otp_mod.
Some OpenTripPlanner instances put the REST interfaces for the router interfaces behind a fixed URL, so that /routers/default is not available. Such as TriMet with https://maps.trimet.org/otp_mod.