java-dest: updated elasticsearch destination's sample config.

Following options are available:
- server: the name or ip address of the elasticsearch server (default: localhost)
- port: the port number of the elasticsearch server's native client port (default: 9300)
- cluster: name of the cluster (no default, required)
- index: name of the index (no default, required)
- type: name of the type (in sql table) (no default, required)