added rendering hints to help with pixel art scaling

[rachel-mp4]

Nearest neighbor interpolation is about 10x faster and looks much better than the default bilinear interpolation when scaling up pixel art, so I added a method on GraphicsObjects that allows you to set the mode. RenderingHints also allows for bicubic interpolation so I added that too, but personally I can't tell the difference and its about 10x slower than bilinear interpolation so I'd be okay with not including it, because it could end up being more trouble than its worth if someone abuses it. Then this method could accept a boolean instead of a string. But all I can say is my group would've really appreciated having nearest interpolation for our 127 final project because it felt unnecessarily challenging to work around, and I think it would be cool to introduce students to tradeoffs in rendering because woah graphics how do computers count so fast