Add Stream Tracking

[rzvoncek]

This issue tracks the work related to adding the capability of tracking Cassandra streams to Reaper.

A draft of this functionality has been proposed in #392. Based on the review of @adejanovski and @michaelsembwever, here are the needed improvements:

• The newly added POJOs must truly be POJOs:
  • FileProgress should be make private.
  • Any method that is not a getter/setter should go to a factory class:
    • Most notably Stream::newStream and Stream::streamId.
    • But also <add|update|finalize>Stream() in StreamSession.
    • Fields and classes should be made final wherever possible.
    • Guava precondition checks should be placed where appropriate, notably for StreamSession fields.
• Streams from all C* versions should be tracked.
  • In the MVP, streams are tracked only in 2.2.9 and later.
• Persistent stream notification listeners.
  • Subscription to stream messages should got to JmxFactory. The current placement in StreamManager doesn't re-establish the listener when reaper is restarted.
• Make stream tracking configurable.
  • It should be possible to configure things like number of threads handling stream notifications and cache retention via Reaper's YAML.
• StreamBuilder should be package protected.
• The @Path in cluster resource may not need the /cluster/ part.
• Use @Alpha for anything that's not tested
• Handle lost notifications.
  • In addition to listening to notifications, Reaper should sometimes also pull stream info to ensure it has correct stream information.

Once the above is done, this should happen too:

• The stream info should be stored in a distributed storage so that a multi-instance Reaper deployments offer consistent streaming info.

[rzvoncek]

Done in #465.