Renamed functions and structures to GLES (rather than GL) to avoid confusion with the OpenGL renderer, which prior used the same names. Removed references to GL_IMG_texture_format_BGRA8888, which will not be supported here. Made it so renderer no longer caches texture filter mode, because I think that is actually bound to specific textures, so we'd need to cache the currently bound texture too ... I don't want to go through that trouble. DOES cache blend function though.