Valhalla default walking speed

[azarz]

Bug

The scripts run in route_graph_generator create graphs with a walking speed of 4 kmph by default. Valhalla uses a walking speed defined by query, with a default of 5.1 kmph (https://valhalla.github.io/valhalla/api/turn-by-turn/api-reference/#pedestrian-costing-options)

We should add here a costing option to have a walking speed at 4 kmph.

road2/src/js/sources/valhallaSource.js

Line 284 in 0e06922

for (let i = 0; i < constraints.length; i++) {

Later, we could add a new parameter in the API, that may be used by all engines for pedestrian routing.