Nested Query support

DSL support for nested queries on the already supported nested type.

>Nested objects/documents allow to map certain sections in the document indexed as nested allowing to query them as if they are separate docs joining with the parent owning doc.
>
> One of the problems when indexing inner objects that occur several times in a doc is that “cross object” search match will occur.

http://www.elasticsearch.org/guide/reference/query-dsl/nested-query.html