couch db replication using /_replicator db instead of /_replicate endpoint

replicate_db.json

{
   "_id": "whatever",
   "source": "http://some.couch.url/dbname",
   "target": "local_dbname",
   "continuous": true,
   "user_ctx": {
       "name": "user",
       "roles": [
           "_admin"
       ]
   }
}

note: must have roles array with "_admin" in order to replicate views.

Unlike when you POST to the /_replicate endpoint, where you can add a "cancel": "true" property to end replication, this replication is canceled by DELETE-ing the doc created in the /_replicator db.

Note: you cannot directly alter documents in /_replicator with {"status": "triggered"}. Delete and recreate the document.