Add new Elasticsearch client as an alternative to the existing REST-clients

[sothawo]

As a first step before switching to new new client it should be added as an alternative to using the RestHighLevelClient and the existing reactive client.

[hartmut-co-uk]

this is about moving to https://github.com/elastic/elasticsearch-java?

[sothawo]

sure. I am currently working on adding the new client as an optional alternative for the next minor version (4.4).

[hartmut-co-uk]

thanks, I guess this also would be brought forward to an ~M2/RC of v5?
(org.springframework.data:spring-data-elasticsearch:5.0.0-M1)

[sothawo]

when it's in the main branch, it then will also be in the next v5 version.