Here is a update with a cool new feature.
I added a shop, that can be created as normal
player. You can add your items to your shop and sell
them to other players until the shop is empty.

Commands:

/removeSpawner

Removes a spawner from a shop

Playershop:

/createPlayerShop <shopname> <size>

Creates a shop.

/deletePlayerShop <shopname>

Removes a shop

/addPlayerShopItem <shopname> <material> <amount> <slot> <sellPrice> <buyPrice>

Adds a item to your shop. If you want to sell the item only set buyPrice = 0 and vice versa.
For material name see below.

/deleteItemFromPlayerShop <shopname> <slot>

Removes a item from you shop
BE CAREFULLY: All items in the stockpile will be deleted.

Refill/Fill shop:

To refill your shop sell your items to your own shop.
You don't pay for that. To see how many items are in
your shop press the middle mouse button. To come
back to the norman view press again.

If you find any bug, please let me know.