De-hardcode barter gold amount property to be more flexible (Variable barter amount for merchants)
In Vanilla MW, merchants have a fixed amount of gold to barter which gets reset each day. For the sake of realism, the amount of gold to barter each day might be different from day to day. As an example: Vasesius Viciulus in Molag Mar has a standard amount of 1000 gold to barter in Vanilla MW. This amount could vary in OpenMW from something like 200 up to 1800.