This will add functionality to automatically load ES plugins

This will setup and load any ES plugins and parses the configuration options for it
It also adds the client ( node, transport ) options to the configuration hash
The same code is used in two differents places.
It could probably be refactored into a class method and a block.

see https://github.com/logstash-plugins/logstash-output-elasticsearch/pull/3/files#diff-e1eda60fc5950f2a16e1209545609fdfR231