Elasticsearch Output Actions

Added 2 new actions (update, upsert) for Elasticsearch Output

If Update or Upsert have no _id and no _type given, a fallback to action 'index' is provided

The Update and Upsert bulk_ftw function produces and ouput like described here:
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/docs-bulk.html

open requests for this feature:
https://logstash.jira.com/browse/LOGSTASH-2200
https://github.com/elasticsearch/logstash/issues/1504