naming convention for elastic search indexes, independent from logstash or any elastic beats.

We should decide how to name elastic search indexes for GeoServer in a way which is independent from logstash or any elastic beats.
we should avoid using patterns like:

```
filebeat-*
logstash-*
```

something like:

`geoserver-%{[metadata][client_name]}-%{[@metadata][beat]}-%{[@metadata][version]}-%{+YYYY.MM.dd}
`

Then we should update index-pattern in default.ndjson.