Replication over cluster

This feature provides to replicate outside the cluster.
A set query cloned by the post proxy query is transferred to the specified server at the post proxy.
In addition, all of the stored data will be transported at the beginning of the cluster replication.
If the concurrency has been changed and reload is requested, the server stops forwarding for the short period of time and transfers the whole database again. I think this feature assumes that the destination is empty at the start time and this code might violate it.