Route medatata: Distance from indicated latlngs, total distance

[gregallensworth]

Relevant to #13 one of the UI items depicted, is that when one finds the nearest segment to the starting and ending latlngs, they will also want to know how far away they are from the trail/route.

As long as we're at it, other obvious metadata to add...

• Decorate the route with metadata (a properties attribute on the document itself) describing the route.
  • Closest point of the trail to one's starting latlng, and distance between that point and the given latlng
  • Closest point of the trail to one's target latlng, and distance between that point and the given latlng
  • Total distance

[gregallensworth]

The structure now includes metadata (a properties on the document itself) of the actual and desired starting and ending points, the distance from the requested points and trail points, and the total mileage. This is documented in the code, and the demo shows their usage in Leaflet.