Expose metadata from Gremlin Server to Clients

To summarize what we have discussed so far:

 1. For API using GremlinRequest/QueryScript, expose response attribute as part of result. Using an approach to similar to Java client driver (using ResultSet) .       [Priority0]
                 -- We rely on the last message for response attributes.
 2. For GLV, add response attribute as part of Traversal. [Priority 0]
                 --Rely on the last message for attributes.

3.  Expose other server details (like server setting).  I would suggest to split this design discussion into two directions:
              a. Metadata for request execution: Only focuses on details related to request execution. Can be achieved through #1 and #2.
              b. Metadata for Gremlin Server:  Focuses on overall metadata for the server. Could be a separate request and fetch the data once for a connection. 

 Targeted drivers: dotnet, Java, python, javascript.

More details: https://lists.apache.org/thread.html/fd2208a2db827bc1eb479ad8c2f181bd2fa532553c97b3fe6994a7b6@%3Cdev.tinkerpop.apache.org%3E