RELAY2: everyone can be a site master

The site master can become a bottleneck if we have a lot of traffic between sites. Also, forwarding messages to a local site master and the site master of the target site forwarding messages to the final destination generates additional traffic.

Therefore, allow every member to become a site master:

• Every member joins the local cluster (site) and the global cluster
  • Everyone (as a site master) maintains a routing table that consists of target sites ("sfo") and a list of site masters
• When a message is received whose destination is SiteMaster("sfo"), we pick a random member of the list for "sfo" and relay the message to it
• The target site master then receives and possibly forwards the message to the final destination (if it isn't the final dest)

Not sure yet if this will be a new protocol (RELAY3) or whether RELAY2 will be enhanced.

Also, investigate whether it makes sense to make only a subset of the site nodes site masters. This would still require local forwarding from non site masters.