Avoid line crossings

[ralucado]

Make line segments avoid each other instead of crossing each other. Once a crossing between three consecutive stations has been found, it can easily be removed by regenerating the inflexion points in between each pair of stations in the reverse order so that the diagonal segments of each path generate from the other station.

Some material: how to check if two segments cross and also a proposed algorithm for making the checks.

[ralucado]

What should the behaviour be between segments of different line? (i.e. should an inflexion point's generation take into account other lines' crossings?) Need to define an appropiate behaviour before implementing anything.