remove debug code.
cleanup code.
* add support API: GET /_api/replication/applier-config
(getReplicationApplierConfig)
* add support API: PUT /_api/replication/applier-config
(setReplicationApplierConfig)
* add support API: PUT /_api/replication/applier-start
(startReplicationApplier)
* add support API: PUT /_api/replication/applier-stop
(stopReplicationApplier)