[Art] Add an option to enable dynamic lighting & shadows

[Sky_walker]

Add an option to enable dynamic shadows from point light sources (electric lights).

And before someone says "OMG it's expensive on hardware!" - I know. But there are people that run Kerbal at 80+ FPS and could benefit from better visuals, while at the same time - it's pretty much the cheapest trick you can get to improve visual fidelity of a game.