Change map view chain and rail signals to have different shapes

[Thinkingwithportals]

When viewing signals in map view and the signals filter turned on, any signalling is a green/yellow/red circle.

I suggest distinguishing the shapes, such as by making rail signals shown as diamonds or triangles. Any shape distinct from a circle, anyway.

I believe this will make it easier to diagnose signalling issues via map view, rather than having to zoom in on individual intersections until the fully detailed view is shown.