clarify threshold types in game

[FluffierThanThou]

Reported by: Fluffy
Description:
@Nachtus01: No, you're misunderstanding the way the thresholds work. If you want to keep a stock of 250 wood, the job should be active when you have less than 250 wood. You should therefore set it to 'less than 250'.

I can see that this might not be very intuitive, I'll have a look at making the language a bit more clear.