GUI themes

The optional background color was extended to entire color themes which there are seven to be choose from. Some areas still need to be adjusted as there were only static colors, but it's been such a fun actually compared to more generic game programming. Color themes surely makes the game look different and there are those lower contrast choices that was discussed. It was surprisingly easy to match background colors for the font colors. Only black was problem and still kind of is in the default black theme (black font on black background) but a viable workaround was a brighter reverse type shadow for that font color.