Simplify the config to only cite a given port once

[Athanasius]

Currently the Gateway has its "where listeners connect" port defined, which is then where the Monitor and Relay connect. That means the same port is defined in 3 places, and you must update all three to have a correctly configured cluster of services.

We should probably change all such to only define the port once so as to make reconfiguration less prone to error.

If needs be we can add CL args to override this.