Allow better query handling of nested fields

[mdavis95]

Consider the sample document:

{  
   "id": "123",
   "title": "The best title",
   authors: [
      {
          firstName: "Tom",
          lastName: "Jones"
      },
      {
          firstName: "Jennifer",
          lastName: "Smith"
      }
   ]
}

Currently it is possible to search authors.firstName:"Tom" AND authors.lastName:"Smith" but that would erroneous match the above document because the matching it is at the root document level.

Using Lucene's blockjoin, it is possible to index child document alongside the parent document and allow separate queries against the child documents.

Zulia should support defining authors as a nested type and then allow searching on firstName and lastName correctly within that nested type.