Construct a new VoidMergeClient.
Get this node's "peerHash" at which messages may be sent to this node.
Set a message callback for handling incoming message data.
Set the ShortCache to use when fetching VmObjSigned data.
It is recommended to use the same short cache across all clients to ensure the memory usage is bounded for the entire application.
A VoidMergeClient can talk to VoidMerge servers.