Migrate Elastic search data from 5.6.4 to 6.6.0

elasticsearch cassandra-3.0 janusgraph gremlin-server elasticsearch-6

We can achieve this by importing the graph data in gryo/json/graphml format. The Practical Gremlin book has lots of examples of using Gremlin's io() step for example - kelvinlawrence.net/book/… Gryo specific usage with io() step can be found here: tinkerpop.apache.org/docs/current/reference/#gryo