Play random demo

[Assassin]

At the moment the recorded demo's always play in the same order in the main menu, I believe alphabetically, meaning you always see the beach2 demo and never any of the other ones. This is really trivial, but it would be nice if the demo played would be random.

[Violet CLM]

Good idea, thank you! I've implemented this for 7.0... that won't come out for a while, but that's when we'll have sufficient control over the menu system to make this easy.