UFO:Alien Invasion Code

* crushed png files

* Reduced filesizes of the tex_lights texture folder by compressing/optimizing the files with pngout

* WIP alien base and a new set of general use lights

* 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