ENGCOM-4389 Elasticsearch6 implementation

Author: ishakhsuvarov

app/code/Magento/Elasticsearch/composer.json

@@ -12,7 +12,7 @@
         "magento/module-store": "*",
         "magento/module-catalog-inventory": "*",
         "magento/framework": "*",
-        "elasticsearch/elasticsearch": "~2.0|~5.1"
+        "elasticsearch/elasticsearch": "~2.0|~5.1|~6.1"
     },
     "suggest": {
         "magento/module-config": "*"