quiet maven warnings
Add MongoCollectionClient.createDefaultFindOneCommand() for convenience.  Modify the semantics of setKeyField().
Rework the creation pattern for mongo connectors.
Details:
* Merge the notion of client into that of a connector.
* Rename MongoConfigurator to MongoConfiguration.
* MongoConfiguration has a singleton instance, that the connector constructor picks up by default.
* MongoConfiguration is no longer responsible for consolidating connectors.  The driver takes care of that underneath.
simplify toString
Merge branch 'je_mongo' into dev