Automatic discovery of Primary/Replica cluster

The use-case of this feature should be clarified. Two possibilities come to mind:
1. A replication cluster (even if just one server) is already running, but servers are not configured in MaxScale. DBA wants an easy way to configure all servers at once so they are in MaxScale and monitored.
2. DBA wants to add or remove servers from an already monitored cluster.

Original description:
Currently the servers to be monitored by MariaDB Monitor must be explicitly listed. In the case of a simple primary/replica cluster that is quite unnecessary as all needed information can be obtained by probing the servers. Basically the only thing the monitor needs to know is the address of one server; after that it can find the rest. If a new server is added to the cluster, the monitor could notice that and act appropriately.

If a service then is configured with the cluster argument pointing to the monitor, it would be very simple to get the system up and running. All that needs to be provided to the monitor is the address of one server and the monitor would figure out the rest.