Introduce Stream Factory Metadata & Resolver

- stream factory metadata is used to manage environment related setting. e.g. zookeeper servers, bookkeeper ledgers path
- stream resolver is used to resolve location of given streams. current supports zookeeper-based bookkeeper resolver.
  it means that metadata is stored in zookeeper while data is stored in bookkeeper.
Add SSN, StreamSegmentMetadata, SegmentsMetadata
Add SSN, StreamSegmentMetadata, SegmentsMetadata (missing file)