Optimize NormalizedNode streaming by using a shared dictionary

When a NormalizedNode is streamed either for Persistence/Replication we encode it such that each streamed NormalizedNode contains a String Dictionary which is unique to a specific instantiation of a NormalizedNodeOutputStreamWriter. Since a shard essentially replicates and stores data for a specific subset of the total yang schema it is not optimal to have this per-instance dictionary persisted and replicated.

Using a shared dictionary when streaming a NormalizedNode can significantly reduced the storage and network bandwidth requirements for streaming a NormalizedNode.