UFO:Alien Invasion Code

* Reduced filesizes of the tex_nature textures folder by compressing/optimizing the files with pngout

* Optimized filesizes by using indexed colors (8bit)

* [TEXTURE_.MAP_RESCALE-tex_nature/rock007-0.25-0.25]
* Rescaled all rock007 textures on all map files and prefabs (TODO:repeat this operation in data_source)
* Replaced unlicensed rock007.jpg texture with a selfmade 1024x1024 pixel version (was 256x256 before)
* Added optimized, new rock007 normalmap (already done 2 commits before)
* Updated LICENSES