Track laying

As proven in https://github.com/Insprill/dv-mapify/commit/5a16da32279c7f975fcb91d12dd5ce6939770aaf, the ability to lay track at runtime, similar to Railroads Online, is possible. This opens up the possibility of creating maps where the player must lay all the trackage required to get from station to station. In practice, this could look something along the lines of the following.

When players want to place trackage, they get the comms remote, and select "Build Track". They would then be able to scroll through the different types of tracks to place (e.g. track, switches, turntables, buffer stops, etc). Once selected, the player will get a live preview of where the track will be placed using a simple ray trace straight out from the camera. For trackage like turntables and switches, simply clicking again with the remote will place it. For tracks, clicking with the remote will mark the start of the spline, and the player will then get a live preview of the entire track from the starting point, to where they're currently looking. To adjust the points of the spline, there can be customizable keybindings in the mods settings menu. To ensure tracks connect properly, if the live preview is within a meter or two of another piece of track, it'll snap to it.

After a piece of track has been laid, there will be another mode on the comms remote to assign it a purpose for job generation. This will allow players to build their own yards in industries.

Finally, there will be another mode to delete pieces of track.