Support for aggregations

[VeggieMeat]

Original issue: https://www.drupal.org/node/2503343

We're currently working on a search that implements Elastic's GeohashGrid aggregation feature. So far I have found no obvious way to make this work with this module. I can get the query to return useful results from the server using hook_search_api_elasticsearch_elastica_query_alter(), but the SearchApiElasticsearchElastica service simply ignores the results when building the standard Search API search results.

Short of implementing my own service class, is there a more pragmatic way to use aggregations? Is it on the roadmap for this module?