bootstrap list of routes: correct relations

[cldellow]

When exploring #1, I came across the Grouse Grind: https://www.openstreetmap.org/relation/3177861#map=17/49.37203/-123.09663

It's a discontinuous trail - for some reason, it omits a way that is also part of the Baden Powell Trail (https://www.openstreetmap.org/way/144953659):

We could fix this in OSM...but I wonder if this is a general problem? Maybe we need to detect and flag them, and then try to salvage by inserting an edge (preferably, an edge that exists in OSM!)