No error checking on world creation for port already in use

[sandain]

We should be performing error checking on world creation (or import) to verify that the requested port is not already in use.

[sandain]

We definitely want to check if a port is in use by an enabled world. How do we want to handle ports in use by disabled worlds? If we don't care about checking disabled worlds, what about when a disabled world is enabled?

[conrad784]

The first part in checking for the ports would be showing the port in e.g. mscs status. Often I am in search of an available port for a new world and this would enable me to choose a good port.

For my use-case, disabled worlds often stay disabled forever, I just don't want to delete them, so for me only a warning would be nice.

[sandain]

The mscs ls command returns the ports in use.