Add missing fields to _segments API

[russcam]

Elasticsearch 6.1.0 introduced attributes to the response for each segment in the response of the _segments API.

Also add

• memory_in_bytes
• version
• compound

Example segment response

        "_av" : {
                "generation" : 391,
                "num_docs" : 14,
                "deleted_docs" : 27,
                "size_in_bytes" : 61621,
                "memory_in_bytes" : 7762,
                "committed" : true,
                "search" : true,
                "version" : "7.1.0",
                "compound" : true,
                "attributes" : {
                  "Lucene50StoredFieldsFormat.mode" : "BEST_COMPRESSION"
                }
              },

Deprecate Size