Add features of ReplicaSet

HI, Tyler and Sam.

Please take a look, we done some features for [ReplicaSet](https://github.com/mongodb/mongo-functional/commit/replica-set). 
Also, we implemented them for [PHP](https://github.com/mongodb/mongo-functional/blob/replica-set/php/bootstrap/FeatureContext.php), with use [mongo-orchestration](https://github.com/mongodb/mongo-orchestration). But, future of mongo-orchestration is vaguely.

By the way, we've more them but we don't sure about behavior of some scenarios.