App: Navigation improvements

[devemux86]

@rumbrummer

You have to reach each Via point, before the switch to next route leg is done (a leg is the part from one Via point to next Via point) - a manual switch by skipping next ViaPoint is possible.

This is already available with “Strict navigation” option.

Kurviger allows to start the strict navigation anywhere,
then you must pass the waypoints in the correct order.

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@devemux86

Navigation currently cannot start on the last route leg (after the last waypoint).

This is to help with complaints that navigation ends when it starts in round trips,
because start and end points are near, so the exit and entry paths are the same.

Perhaps this could only be active in “Strict navigation”.