`objectscript.conn.docker-compose` feature fails if container doesn't expose its superserver port

[gjsjohnmurray]

This was caused by #1485. I propose adding a way to indicate that no superserver port should be sought.

    "objectscript.conn": {
        "docker-compose": {
            "service": "iris",
            "internalSuperserverPort": 0
        },
...

[isc-bsaviano]

@gjsjohnmurray Can the code that does the discovery fail gracefully automatically instead of requiring that the user set a setting?