new transportation option

[tkobo]

Supply path - dirt path on cut thru the terrain, that gives no travel perks, but allows supply to spread along faster then regular terrain, but not as fast as road. Should build much faster then road.

[tkobo]

I think theres an easier solution, just have road construction pass along supply at a rate reduced from completed road, but better then empty hex.

[StephaneDurette]

makes sense! looking into it,
ticket 26717