Index Full nested document Hierarchy For Queries (umbrella issue)

Solr ought to have the ability to index deeply nested objects, while storing the original document hierarchy.
Currently the client has to index the child document's full path and level to manually reconstruct the original document structure, since the children are flattened and returned in the reserved "_childDocuments_" key.

Ideally you could index a nested document, having Solr transparently add the required fields while providing a document transformer to rebuild the original document's hierarchy.

This issue is an umbrella issue for the particular tasks that will make it all happen – either subtasks or issue linking.