Creates a new group of worlds with the given name and starts it in a new thread.
* This method only creates a group, which is a container for worlds, but no actual world.
* To create a world the addWorld method must be used.
* Example:
* ---
* auto group = server.addWorldGroup("MyGroup");
* auto world = server.addWorld(group, 0); // where 0 is the seed
* ---
Creates a new group of worlds with the given name and starts it in a new thread. * This method only creates a group, which is a container for worlds, but no actual world. * To create a world the addWorld method must be used. * Example: * --- * auto group = server.addWorldGroup("MyGroup"); * auto world = server.addWorld(group, 0); // where 0 is the seed * ---