Upgrade to ElasticSearch 1.1.0

ElasticSearch is currently at version 1.1.0. The patch attached upgrades the dependencies, fixes a couple of changes required by 1.1.0 and also :

• removes the need for having ES in the main ivy dependency - it is now only required at the plugin level
• improves the logic around using the cluster name or an explicit host:port to connect to ES : the clustername is not required nor set when using host:port
• uses a more sensible default value for the port