Implement Deconstruct for color structs

[hillin]

E.g.

    public static class LChuvColorExtensions
    {
        public static void Deconstruct(this LChuvColor lChuv, out double l, out double c, out double h)
        {
            l = lChuv.L;
            c = lChuv.C;
            h = lChuv.h;
        }
    }

Usage:

    LChuvColor lChuv = GetColor();
    var (l, c, h) = lChuv;

[tompazourek]

Good idea. I think I already noted this some time ago (#41), it's not too difficult to add, and a nice feature.

I hope to get around to this soon. I'd like to release v3 first with the new extensible conversion engine.