UFO:Alien Invasion Code

* base/textures png crush.

* 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

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

* GPL'd and unified tex_buildings/wall027-032

* GPL'd the partner wall for tex_buildings/wall032 as well since it's just a slight adjustment

* Some new textures for an electrical box

* Some new/updated textures

* New advert textures for city RMA