Add params variant of Choose()

[Diamond-Wolf]

Added a new variant of Choose() which allows an arbitrary number of arguments.

[prime31]

So, the problem with a method like this is that you pay the price of an array allocation for the params every time you call it. I'm not sure how good of an idea it is to sneak that into the API. If you have more than 4 options it is probably better to have them in an array/List/FastList and just use a random to get the index.