Button code, incomplete but functional

The button code is not complete, but it works. There's some spaghetti code, and currently there are no constructors to set it up, but it can be done. I'll probably come back and finish this later tonight, but you can merge/finish this code yourself if you want. There are 3 images for the button, one for when the mouse is not over it, one for when the mouse is over it, and one for when the mouse is clicking down on it. It throws an event when the click is released on it. SpriteFonts eluded me, so the text part might not be finished yet.