Weather Roulette Admin v1

This adds an admin section to Weather Roulette at
/weatherroulette/admin/. You can see players' progress for each game there,
rendered as a Highchart graph.

You can lock and unlock games, delete games, and export their data.

All the data importing/exporting doesn't actually work yet. That's what
I'll be working on next.

This commit also contains a refactor of the Weather Roulette game --
Moves are now saved in the database when you start playing a new game.