XD-1270: Add states to the deployment of stream

Summary of changes:

1. ModuleDeploymentWriter now returns ModuleDeploymentStatus
   which encapsulates everything related to individual
   module state.

2. The ModuleDeploymentStatus objects are aggregated and
   passed into an implementation of new interface
   DeploymentUnitStateCalculator which calculates the
   state of the job/stream based on the individual module
   states.

3. Interface DeploymentUnit was introduced to cover the
   common attributes for streams and jobs.

4. The status for streams/jobs is written into ZK under
   /xd/deployments/streams/<name>/status and
   /xd/deployments/jobs/<name>/status, respectively.

5. As a result, modules for streams and jobs are now under
   /xd/deployments/streams/<name>/modules and
   /xd/deployments/jobs/<name>/modules, respectively.

6. The stream and job repositories have a new method
   getDeploymentStatus which may be invoked to obtain
   the state of a stream/job.

7. Stream and job states are recalculated when a container
   joins or leaves the cluster.

Addressed PR comments