Replicator timeout (#2480)

* Add timeout to Replicator::new; used when polling for leader

* Add timeout functionality to replicator ledger download

Shares the same timeout as polling for leader

Defaults to 30 seconds

* Add docs for Replicator::new

replicator/src/main.rs

@@ -82,7 +82,7 @@ fn main() {
 
     let leader_info = NodeInfo::new_entry_point(&network_addr);
 
-    let replicator = Replicator::new(ledger_path, node, &leader_info, &keypair).unwrap();
+    let replicator = Replicator::new(ledger_path, node, &leader_info, &keypair, None).unwrap();
 
     replicator.join();
 }