Randomize player colours at the start of each game

[EvanQuan]

Because colours are fun, and choosing your colour is too much work (given our time frame).

[EvanQuan]

@jamescote Everything is good, except for the hovercraft texture not being randomized. eg. Player 1 will always be red, player 2 blue, etc.

[jamescote]

I'm not sure it's a big issue, but I suppose it could be changed. It would be done in the sceneLoader for createplayer. Just randomize the index for the Hovercraft properties.