UFO:Alien Invasion Code

* Reduced filesize of the tex_buildings textures folder by compressing/optimizing the .png files with pngout

* Converted some textures to indexed colors (8bit=256 colors) to optimize filesizes and improve loading performance

* Replaced tex_buildings/concrete012-021 .jpg textures with high quality .png versions (Note: quadrupled resolution for all of those textures, some are unused though and some do not have and did not have power-of-2 resolutions [concrete014-018 and 020-21])
* Updated LICENSES