Limit growth of kenshi.log

[mdh]

As of 1.0.31, my kenshi.log has been growing quite a bit. After about ~40 hours of in-game time, it had reached 50GB in size and I keep having to manually delete it every once in a while. It might make sense to roll over the kenshi.log file when it reaches a limit (maybe 100MB or so?) in order to prevent it from just filling disks.