UFO:Alien Invasion Code

* Recompressed all textures in base/textures/tex_base with Trimage image compressor and commited those files, where a filesize reduction of at least 5% (up to 81.5%) was achieved

* Reduced filesize of the tex_base 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 lab_floor001-002 and lab_wall001-003 .jpg textures with high quality, high resolution .png versions (lab_floor1.png has the same resolution as the old .jpg), updated LICENSES