Move TOCropViewControllerAspectRatioPreset to a class and make it configurable

[glyuck]

Now it's possible to use completely custom aspect ratio presets:

    cropViewController.allowedAspectRatios = [
        .init(size: CGSize(width: 1024, height: 768).normalized(), title: "Landscape"),
        .init(size: CGSize(width: 768, height: 1024).normalized(), title: "Portrait"),
    ]

Don't forget that aspect ratios need to be normalized (i.e., the width and height of the size should be in the range [0..1]).

private extension CGSize {
    func normalized() -> CGSize {
        if width == height {
            CGSize(width: 1, height: 1)
        } else if width > height {
            CGSize(width: 1, height: height / width)
        } else {
            CGSize(width: width / height, height: 1)
        }
    }
}