Permanent item listings#23

Add a new permission, playershopguiplus.permanentlisting and a new command /pshop perm sell [quantity] [price]. This would allow us to add permenant items to the player shop. These items would never run out of stock and would never get removed from the shop without removing them. The person who listed the item could remove the items from the GUI.

This suggestion was migrated from old suggestions made at the Discord server.