Add ElasticSearch as s-c-s sink

[sabbyanandan]

From @sabbyanandan on May 6, 2016 17:9

From @sabbyanandan on January 19, 2016 17:58

As a user, I'd like to have an option to write to elasticsearch sink, so I can aggregate, search and analyze data insights in real-time. This can be adapted from @mbogoevici's POC here.

Acceptance:

• elasticsearch as sink module is available in spring-cloud-stream-modules repo
• maven repo includes elasticsearch module with respective group/artifact/version detail
• documentation included in SCSM reference guide

Copied from original issue: spring-cloud/spring-cloud-stream-modules#159

Copied from original issue: spring-cloud/spring-cloud-stream-app-starters#70

[unhappydehare]

Now, elasticsearch has been used for log storage and retrieval in many scenarios. Suggest to add Slink support for elasticsearch? Or should we use SpingDataFlow as the middleware for log processing.