Worker changes
Added worker walking speed penalty that applies after 30 tiles and ramps up slowly over distance. This is a very lax restriction on worker effectiveness over distance that is intended to prevent cheesing by using workers to move goods between industries instead of using trains. The values may need to be tweaked in the future, but I'm starting with a minimal penalty to avoid breaking many solutions. Values are exposed in balance settings.
Fixed bug in worker pathfinding that would cause them to sometimes not take the shortest path.
Multi-Threading
Made setting thread priorities to be higher than normal an option that is disabled by default. This may account for the stuttering issues that people have reported, especially while streaming. It's generally not recommeded to raise thread priorities, but I thought that since I was only doing so for a subset of processors that it would not interfere with other programs, but this may not have been correct. I still set thread affinities, which is also not generally recommended but is more necessary for correctness due to my using spin locks.
Graphics
Made track rendering nicer by making bridges have thickness and an under-side and the gravel mounds under tracks to also have a rounded thickness appearance.
Added pillars under footbridges and ensure that footbridges remain above water.