Reuse loaded tracks for routing

[nrenner]

Reuse loaded track(s) as basis for or as part(s) of a new route.

Approaches/ideas:

1. append or insert routed segment to track -> combining track and route segments
   • split/remove parts of a track before combining
   • related, but probably different to straight segments (Allow straight lines #68), as a generated/recorded track has too many track points to manually edit (?)
2. convert track into a route (using map matching and reverse routing)
   • handle and combine multiple separate routes (converted tracks)
3. like 2., but instead of editing and stitching together multiple parts like in 1. and 2., draw a new, single, continuous route, using tracks as guidelines and convert and include them as routed segments on the fly
   • while drawing, waypoints snap to tracks nearby, when next waypoint snaps to same track, convert the part in-between into a route and insert its via points to current route

I haven't thought this through, but I guess I would prefer 3. and avoid getting into track editing (1.).

Requests, use cases:

• Load GPX track (comment) · nrenner/brouter-web#30
• Erweiterung der Routenoptionen (BRouter–Google Groups)