Nested included resources filters

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Description

Hi guys, I'm sorry about how this issue is looking, don't have time to make it better.
Currently, (checked on 0.9.5, and it's probably the same on 0.9.7) filtering on nested resources works only for 1 level deep inclusion, i.e. included_resource.filter_key. I made some monkey-patches in my app, to make it work with nested resources inclusion, i.e. included_resource.another_included_resource.filter_key.
Also, I did some changes to make filters work with has_one relationships.

The code can be a little bit messy, but it's working, at least for my project. No blame, please :)

The code is here: https://gist.github.com/RoM4iK/1ce4eab45ed0ceafa8728ed487ccddbb

Empieza revisando el Gist enlazado y localizando el punto de entrada existente para el filtrado de recursos en el repositorio. Compara el comportamiento actual de los recursos anidados en un solo nivel con la anidación más profunda solicitada y las relaciones has_one. Se considera completado cuando los filtros anidados funcionan en varios niveles de inclusión, incluidos los recursos has_one, y los tests del proyecto cubren este comportamiento.