Add aggregation support on content views configuration

Aggregates configuration should be added to content view configuration.

• a checbox allows to specify "aggregation support"
• when checked, a new layout is displayed to the user, similar to the search layout is added
• a typology of accepted aggregates should be added to Studio contributions:
  • cardinality: http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-metrics-cardinality-aggregation.html
  • histogram: http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-bucket-histogram-aggregation.html
  • date histogram: http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-bucket-datehistogram-aggregation.html
  • "generic" agregation, passing through json-like information directly to elastic search for complex use cases ("free" configuration")

When user choses a schema property, accepted corresponding aggregation types are available.
When chosen, needed properties for this aggregation are filled by user