Extract the day route builder out of useRouteCalculation into a pure module and
aggregate it over the whole trip: one map with every day's route, each day in its
own colour, the mode per stage and the trip's total distance. Straight lines first,
roads as they answer; a refused leg keeps its line and adds no distance.
Give the floating map controls one shared drop shadow while adding the toggle, so
the new pill and the base-layer switcher stand off the tiles the way the locate
button always has. Document the control in wiki/Map-Features.md.
Addresses #1736
Konstantinos Thermos