Use aggregations for grouped types

[Xon]

Threads can be considered an aggregates of posts, but due to how Enhanced Search stored posts vs threads, this makes search useless to find a given thread which contains some post contents without spamming large number of posts.

This makes the return results less accurate, and need to query the db for lots of useless information.

Some info:

• https://www.elastic.co/guide/en/elasticsearch/guide/current/top-hits.html
• https://www.elastic.co/guide/en/elasticsearch/guide/current/aggregations-and-analysis.html
• https://www.elastic.co/guide/en/elasticsearch/reference/current/_executing_aggregations.html