Inclusion/Constraints on use of international fuels when limited amount of regions are modelled

[maartenbrinkerink]

For future versions of the model (post-paper), we have to include international fuels that;

• can be used even when the source countries for the international fuels are not modelled
• are somehow constrained as such that not all international fuel can be used by the countries that are modelled (a size dependent relationship should be integrated based on e.g. relative electricity demand of the modelled countries vs full global demand).

[maartenbrinkerink]

Moving this to Longer term developments as this is not a straight-forward implementation for which we have the bandwidth within the GGI Finance project.