- Fix normal vectors/lighting for train tracks.
- Adjust chat command logging statement.
- Remove train tracks when their chunks get unloaded.
- Create a struct for the 6-tuple returned from `get_nearest_ways`.
- Move code that creates the train tracks into `layers::apply_trains_to`.
- Implements mesh generation for cylinders and lines.
- Implements an Id-allocator so that clients can mutate positions efficiently.
- Is split into pipeline and scene modules.
- Contains simple shaders that just pass through a position and color.
