Frontend: * Avoid overwriting/replacing premade game/weapon schemes

fix iphone version for map preview add gl_priority constant (doesn't affect opengles) fix building hwlibrary

map preview generation reworked like nemo suggested (he was right, it's quickier in this way) add some rounding image capabilities for more professional look

Engine: * Added texture priorities to try to keep often used sprite textures as well as huge textures in video memory - this should improve performance on systems with low video memory * Fixed portal gun's weapon offset