Redone the whole rendering mechanism. The renderer class now has a global instance and offers a simple API for basic rendering operations and the widgets render themselves using said API. This way less static casting happens while rendering, it's easier to extend and it's simply better OO style.
Also a resource management was introduced. It also has a global instance for easy accessibility but local instances are still allowed (no, not a complete singleton). Resources don't have to be initialized, they just get loaded the first time someone requests them individually. This concerns textures, fonts and sounds.