[WIP] Added a Replicator object

This is a work in progress for the Replicator object. It can successfully create a replication -- next steps are to fill out and test the stubs for getting replication status, getting all replications, etc.

Would like some feedback to verify that I'm going in the right direction with this, though.

@ksnavely @evansde77 @jcounts @dmannarino 
@evansde77: Yes. An alternative would be to pull out the authentication info from each database ... but that's poking around in more private methods, and I fear the wrath of pylint, even if I'm a bit cavalier about using private methods myself :-)