Changes for new font rendering approach in nifty, using separate resizable texture for each font

Part of a big conversion to use multiple textures in font rendering for faster rendering. Changes in nifty require this changes of font renderer interface. Also, glyph atlases have been deprecated in favor of nifty-sided resizable textures; i.e. now is only a single glyph bitmap data is generating at a time, also improving performance on CJK unicode pages.