Pull request to add group support and singleton chest

Hey Mtihc,

Don't worry if this is to late, I should have sent this request a while back.

I think other uses of treasurechest might find these enchantments useful, the main drive behind them is to allow tchest to be used in events and reduce the setup time by being able to create groups of chests all of which can be controlled via a single command.

Singleton chest support was added for events as well to keep the incentive for players to find a treasure 1st and be able to restrict the number of treasure items in a map globally rather then per-player.

Cheers,

basicmark