Power Grid Overlay improvements

[Kasuha]

Since there's important difference between Heavi-Watt Wire and standard Electric Wire now, the power grid overlay should show us which part is made of which, e.g. through thickness of the line used to draw the grid, or by giving the heavi wire an outline. Most of my electric lines go through walls or floors, it's not easy to remember what I used where and checking it tile by tile using mouse is cumbersome. Sure it's possible to use the heavy wire everywhere once you research it. but I think that's not the point of the game.

Also, it should show parts of the grid that are switched off (i.e. contain only consumers and no producers), e.g. using grey line color. I liked that feature a lot on the previous release.