logic: load 6 skybox textures when shader gets used by scene, don't unload dynamically, just on 'flush' texture browser only uses normal preview image and doesn't trigger potentially heavy box loading also fix R_ResampleTexture for [2+x upscaling
git-svn-id: svn://svn.icculus.org/netradiant/trunk@60 61c419a2-8eb2-4b30-bcec-8cead039b335
git-svn-id: svn://svn.icculus.org/netradiant/trunk@56 61c419a2-8eb2-4b30-bcec-8cead039b335
git-svn-id: svn://svn.icculus.org/netradiant/trunk@1 61c419a2-8eb2-4b30-bcec-8cead039b335