Production queue - change BuildTimeSpeedUpDivisor

This is needed. The current integer parameter was limited - we could never have less than a 50% build speed reduction.

I `grep`ed for mods using this yaml setting and found none.

**Note: This does not enable it for any mods**

- Now is a yaml setting where you can set the decay in %, e.g. 100, 85, 75, 65, etc. So the second production building reduces time to 85% of original time, third 75% of original time, etc.