Extend SASL protocol to handle Quality of Protection

SASL implementations generally provide authentication and encryption services to communication protocols.

At present, the JGroups SASL protocol layer handles only authentication of a client joining a group; it does not support encryption of messages (unicast and multicast) passing through the SASL layer. This is presently handled by the separate ENCRYPT layer.

It would be nice to provide an integrated and complete solution for authentication and encryption for JGroups based on SASL. This could be achieved by adding functionality from ENCRYPT to the SASL layer.