interface modification
validate interface
Merge branch 'develop' of https://github.com/Stratio/stratio-connector-elasticsearch into develop

Conflicts:
	connector-elasticsearch-core/src/main/java/com/stratio/connector/elasticsearch/core/engine/ElasticsearchMetadataEngine.java
	connector-elasticsearch-core/src/test/java/com/stratio/connector/elasticsearch/core/engine/ElasticsearchMetadataEngineTest.java