Estimate duration and possibly other data about route

[dittaeva]

While looking for something about accumulated ascent/descent for issue #112 I found an article about calculating hiking duration, and saw that cyclestreets calculate journey time, calories, co2 avoided, and quietness. In addition, we have a project at WNRI where we're going to calculate difficulty according to a new Norwegian hiking grade standard and probably also duration according to the standard used by the Norwegian Trekking Association.

In addition to choosing the standard for estimation, and how to do it, there are challenges with not really knowing start/end of route, different calculation methods for different route types, and possibly taking into account other factors such are surface type, etc. Things normally done by a route calculation engine.