Verify Elastic Search plugin on 1.5.22-alpha

Available documentation:

https://peerplays.atlassian.net/wiki/spaces/PROJECTS/pages/1159299078/Quick+setup+of+Elasticsearch+on+AWS+and+connecting+a+witness+node+to+it

https://peerplays.atlassian.net/wiki/spaces/PIX/pages/364609555/ElasticSearch+Plugin+for+Peerplays

https://peerplays.atlassian.net/wiki/spaces/PROJECTS/pages/1367113733/Quick+setup+of+Elasticsearch+plugin+on+local+computer

cc @tai.sama : We may need this plugin for the explorer's REST API.