Adding output to the mongo-out nodes

[ozomer]

The node-mongodb-native package is using callbacks for the write commands, with values that can be useful. For example, when a save command finished and we want to know if it inserted a new document or updated an existing one - the callback is called with the new document on inserting or with 1 on update.

I agree that when a callback is called with an error, the error should simply be logged.