[core] Fix schema version in jgroups config file
[core] Upgrade JGroups 3.3.1.Final -> 3.4.0.Final
[jvstm-lf] Substitute JGroups for Hazelcast as the group communication system
[jvstm-lf] Substitute JGroups for Hazelcast as the group communication system (part 2)
[jvstm-lf] Only committer thread writes mapping txVersion->commitId