Allowing daemons to stop

[qevni]

Couple of issues which made it very hard to stop and start an express-pouchdb server with active replications in defined in a _replicator document.

• in replicator.js, the db variable was never set, so undefined for db.stopReplicatorDaemon
• callAsyncRecursive typically stops on the first daemon, since it doesn't have a stop method, and thus func[0] === undefined
• The promises set up after replication completion in pouchch-replication fire up right after the daemon gets shut down, and throw exceptions on missing db within dbData.dbs which is empty, when trying to clean up the replication (which already has been cleaned when shutting the daemon down).
  Open to better ways to do this. Thank you!