[STREAMING] SPARK-1730. Make receiver store data reliably to avoid data-loss on exec...

...utor failures.

Added a new method in Receiver, ReceiverSupervisor, ReceiverSupervisorImpl to store the data
and callback a supplied function with a given argument.
Returning a Future[Boolean] does not expose the exception. Maybe its better to return something like a StoreResult that has a boolean field and an exception field. And this change will the API breaking change, so better to do it now rather than later.