WorldMaster

• Prefixes for players: [Player] + [Owner] (If enabled chat message won't be signed and can't be reported)
  
• New welcome text and join, leave message and chat style
• Player counter bossbar
  
• Elevators [/elevator]

Enable flying on server, if used in survival

• Chest Shops: See documentation
• Chunk loader [/chunk_loader]

May produce lag, if you have to many chunk loaders

• Inventory Managment System [/inventory]
• Mulitple Worlds [/world]

May produce lag, if world is created or regenerated

Every world has always loaded spawn chunks which may produce lag

Level-Name in server.properties has to be "world"

• Permission for all commands of the plugin + shop owner permission

Installation

Copy the .jar file into your plugins directory of your server.
Start the server. If the server was already started, type "/reload" in the server console.

Documentation
Documentation on GitHub