Instead of using different modules we use a bukkit profile to test backwards compatibility with pure-Bukkit servers and use the paper-api in the default profile. This should really be done with modules in the future. The actual selection which listener to use is handled by checking if the event class exists on event registration.
This is required as we now move items between inventories instead of individually removing and adding. This basically adds the stock represented by the admin shop sign to the AdminInventory so all transactions should always be possible.
