Lighting and overall brightness tweak

When SC was started the usual apprentice for space in a game was bright and clear, however in recent years this style has faded, and been replaced by darker, more ominous visuals. It is also slightly off putting when there is supposedly an alien horde at the figurative gates and the background is all bright sunshine and golden clouds, not to mention the loss in realism that causes. The game could look much better with darker backgrounds and/or less light all around, a few newer areas (mostly those that have been marked as “destroyed” by the invasion) already fall under the newer style, but are a small minority.