V. 1.8.0

Changelog:

- Spliting a segment now copies over the correct lanes and prefab lines
- Fixed regenerating a road/prefab line/intersection not always triggering unsaved changes, this meant that in some cases Unity though it had save the latest changes when it had not and progress therefore was lost.
- Made it possible to connect two lanes directly after each over, useful if you want a part of the road to have an older asphalt texture for example
- Fixed short lane's lods not starting at the correct position
- Fixed an error caused by short lanes
- Fixed some cases of lane lods overlapping
- Fixed not being able to edit material lists in older Unity versions
- Internal code inprovements