Added some methods for event-handling, Renderer support and Scancode retrieval.

Note that `createWindowAndRenderer` differs slightly from the original method, because a window configuration that contains width and height gets passed in anyway and thus there's no apparent need for extra parameters.
Hm, the way I see it this seems to be mostly a way of explicitly stating that software rendering is acceptable as fallback when accelerated rendering is not available [1]. Doesn't feel like the right answer, though.

[1] https://wiki.libsdl.org/SDL_RendererFlags