Add logistic costs to warfare

[olleharstedt]

Warfare as it is now is not really "incremental" - it's possible to raid a small village an infinite amount of time. My idea is to add a cost for troop logistics, which scale up with the number of troop and the area of your nation. The intuition behind it is to simulate distance, that "the same village" is in fact further and further away. This could also motivate the player to try out harder wars earlier, so as to not increase the logistic cost too much.

[olleharstedt]

It would also be possible to add research objects which decrease the cost of logistics, like trains, cars, horses, etc.