Add support for `foot=use_sidepath` / `sidewalk=separate`

[TheMarex]

Several communities in the US have started to map sidewalks as separate ways, even if they are attached to the main roads. This degrades the quality of our routing as we route on the main road and the sidewalk, generating erratic routes, problems with snapping and blowing up the size of the road network artificially.

There are two tagging schemes that mark roads that have a detached sidewalk: foot=use_sidepath and sidewalk=separate. Roads tagged like that should not be included in the routing graph anymore.