ILP routing table implementation
RouteData refers to the Routes schema in five-bells-shared.
Combine two parallel routes, generating a new curve consisting of the best segments of each.
Compose two routes end-to-end: A→B.join(B→C) becomes A→C.
Shift a route's curve left or right.
Shift a route's curve up or down.
Simplify a route.
Check if a route has expired.
Returns whether or not a new route was created (updates don't count).