Add CoMaps, the offline OpenStreetMap navigator, alongside the existing
map integrations. A geolocated place gains a CoMaps entry in its
navigation menu, and a day's route toolbar gains a button that hands the
day's bookended stops to CoMaps in that day's travel mode.
CoMaps' route link carries only a start and a destination, so a two-stop
day goes as a route and a longer one as named pins rather than silently
losing the stops in between. Links use the https form so a device without
CoMaps installed lands on comaps.at instead of a dead scheme.
The hotel-bookend logic behind the Google Maps export was duplicated
between desktop and mobile; both now share dayExportStops so the two
links cannot disagree about which hotel legs are real.
Addresses discussion #1904
Konstantinos Thermos