Start route with U-turn to make spawn points more versatile

[sandermvanvliet]

Support doing a U-turn at the start of the route to provide flexibility to start riding in Zwift in more directions as some spawn points currently only allow to ride on one direction.

For example in Watopia the spawn point in the desert only allows you to continue in the direction of the Fuego Flats arch.

As RoadCaptain already detects the direction on a segment we can use that to reverse direction and then progress in the other direction.

Not sure if this situation exists in other worlds than Watopia but it should increase the flexibility when building routes.