Add scale_fuel_usage to burner-generators

[KiNg626]

Currently both reactors and fluid generators have the ability to decouple their power generation/fuel consumption from the amount of energy the electrical network they are hooked up to needs, but burner generators have no such option.

[protocol_1903]

Burner generators do this automatically

[KiNg626]

I don't know if it's changed recently, but I just tested this in in 2.1.12 using the built in burner generator, and it definitely does scale it's output and fuel consumption to match the network consumption.