Replace current elasticsearch client with the official one

[SpyrosRoum]

Describe the problem you are trying to solve
Replacing the current elasticsearch client used with the official one may have performance implication

Describe the solution you'd like
Use the official client for elasticsearch, see #411 as well

Notes
The official client doesn't support connection pooling yet but there is an open pr that seems to be close to completion: elastic/elasticsearch-rs#139

[Licenser]

duplicate of #411