UFO:Alien Invasion Code

* base/textures png crush.

* Recompressed all textures in base/textures/tex_alienb with Trimage image compressor and commited those files, where a filesize reduction of at least 5% (up to 92.8%) was achieved

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

* Hi-res version of wall texture for alien base

* new alienbase textures (gpl 2 or later by Nate Wright)

* GPL'd tex_buildings/window001

* Adjustments to tex_material/metal012 and 013

* Some new textures, still need work

* Some flat, tileable concrete and metal textures