Choose signal options

[jamespetts]

In the process of fixing another bug, I have found what was causing choosing up to end of choose signals not to work, and I have managed to get this feature to work now. The train will try to find an alternative route to the nearest of its next stop or the next end of choose sign on its route whenever it encounters a choose signal and the route to whichever is the nearest of those points is not free.

Edit: I have just implemented a change whereby cab signals are treated in exactly the same way as track circuit block multiple aspect signals, save that there is an unlimited sighting distance. For ETRMS style signals with no visible aspects, it is recommended to leave the number of aspects at 2 to prevent reserving further ahead than necessary.