Elasticsearch stabilisation & refactoring

**Note that this breaks Insighgt Hawtio functionality which will be fixed in the next couple of weeks.**

This PR brings the following:

* Configuration factory for Elasticsearch nodes
* Elasticsearch plugins are usable via fragment bundles
* New profile for an Elasticsearch client so only designated nodes in the Fabric have to store data
* Exposure of native Elasticsearch REST API to make it easier to integrate other Elasticsearch tools (e.g. Kibana) directly to Elasticsearch