CLI: expose relay nodes

2 changes are expected in this JIRA

• use "relay node" instead of "site master" or "site coordinator" [1]. It is a better name.
• Expose the relay nodes in the CLI. Example site info would expose relay_node=true/false, local_site=<local site name> and relay_nodes_addresses=<list of node names>

[1] https://github.com/infinispan/infinispan/blob/7852bc6d3de4d6cc380867f1a7cc2bf1f42d3056/core/src/main/java/org/infinispan/manager/CacheManagerInfo.java#L171