UFO:Alien Invasion Code

* base/textures png crush.

* Recompressed all textures in base/textures/tex_nature with Trimage image compressor and commited those files, where a filesize reduction of at least 5% (up to 66.3%) was achieved

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

* Replaced pjrock1, pjrock17 and pjrock21 textures with new, selfmade 1024x1024 pixel versions, updated normalmaps for pjrock1, pjrock17 and pjrock21, updated LICENSES

* added textures/tex_nature/pjrock* normalmaps (except pjrock6, because this texture should be replaced because of quality reasons), you can test most of these new normalmaps on forest maps
* updated LICENSES