Issue Description:

It would be good if there will be a config option for combustion generator fuel registration

What happens:

While there is an IMC registration API for combustion fuels, there is no config option for that. This makes hard to customize fuel system for a modpack developer who is not a Java coder.

What you expected to happen:

A config file (similar for alloy smelter recipes or vat recipes) that allows us to add custom fuels to combustion generator, like Forestry ethanol, IE biodiesel and many more. Yeah, you can expect mod developers for support EnderIO but I think it will less likely happen. If EIO could have a config possibility for this, gamers and modpack developers can speed this process up a little bit.