IList<T> Shuffle extension

[falwickster]

Hi.

I added a shuffle extension which returns items in random order. Although I am not sure how to test randomness, so I added test cases with a very small probability of failure. I hope it will suffice

[JonathanMagnan]

One way to test it would be probably to give a random seed, but I don't think going through this will be very useful ;)

Thank you for your extensions, I will review it and should be soon released if everything is fine.

Best Regards,

Jonathan