Save/import terrain (land) along with the track

[mkruer]

While it would likely be very complicated to implement, I'd love to see the ability to save terrain alongside the track and scenery. This would fix the issues where some rides cannot get imported easily because the terrain is too low to support the track or in other cases where there is a lot of dips inside the ground. Even if this was a destructive import, wiping out anything in the area, it would still be worth it, and then come back and fix those sections the import destroyed.