Use Pterodactyl instead of Multicraft

Facing increased issues with Multicraft, Pterodactyl should be used instead. This is a modern replacement for Multicraft which supports more types of game servers, SFTP and runs each server in its own Docker container (allowing for easier management of Java versions etc.).

The Pterodactyl daemon is called Wings and is easy to install: https://pterodactyl.io/wings/1.0/installing.html.