UFO:Alien Invasion Code

* base/textures png crush.

* crushed png files

* Texture optimizations: reduced file size, resized textures and removed an unnecessary texture from a map

* Recompressed all textures in base/textures/tex_buildings with Trimage image compressor and commited those files, where a filesize reduction of at least 5% (up to 95.2%) was achieved

* replaced wall007 with gpled texture (that is also higher res, so maps are updated, too)