Implement Tutorial

[Spycho]

Probably with lots of popup help, and a cut down world (or several) with just the one avatar in it, before letting the user go through to the main world. This would also help deter people from signing up with loads of accounts, so it should be lengthy and useful the first time around, but arduous the second.

Possibly worth waiting for the game to get more nailed down first, as the tutorial may have to change a lot otherwise?