Load route geoms for line and branch, allowing stations, and produce graph

[alephcero]

User should be allowed to provide a geojson for route geoms with line id, and branch id (if needed). From this, urbantrips should build

• Graph for the whole line (for routing and distances purposes Add distances over the transit network #30 )
• Line geom (compressing or averaging the line for all branches)
• Stops interpolated each x meters

But for modes like train, subway and tram, a stops geojson would be useful as stops are not regularly distributed like buses.

From this a stops table could be built, different from station's catchment area. Related to #27.

Loading, inferring and updating routes should be handle separately #32

[alephcero]

Closed by b61b211