Have the solver make the decision on annual road transport demand

[adrienmellot]

What can be improved?

In the current set-up, we assume full electrification of the road transport demand. Other alternative carriers could also meet this demand in the future ( #273 , #274 ). The solver needs to make the decision of how much is electrified or met by other carriers. For now, let's have the solver make the decision, even though the only available option is battery EVs.

Version

1.2.0.dev