* Initial work on write concern support, set for the lifetime of the session
* Add base64 encoded value support, include docs and tests
* Handle error from json.Unmarshal, fix test and docs
* Remove writeConcern struct, move JSON unmarshal to Initialize
* Return error on empty mapping of write_concern into mgo.Safe struct
* WIP on mongodb plugin
* Add mongodb plugin
* Add tests
* Update mongodb.CreateUser() comment
* Update docs
* Add missing docs
* Fix mongodb docs
* Minor comment and test updates
* Fix imports
* Fix dockertest import
* Set c.Initialized at the end, check for empty CreationStmts first on CreateUser
* Remove Initialized check on Connection()
* Add back Initialized check
* Update docs
* Move connProducer and credsProducer into pkg for mongodb and cassandra
* Chage parseMongoURL to be a private func
* Default to admin if no db is provided in creation_statements
* Update comments and docs
