Support nested queries with Ickle

At the moment it is not possible to express a query that takes advantages from embedded nested entity:

@Embedded(structure = Structure.NESTED)

We want to introduce a new query expression such as:

FROM fax.play.book b
JOIN b.reviews r
WHERE r.score = 8.75
AND r.content : `very`

At the moment the only query we can do is:

from fax.play.book b 
where b.reviews.score = 8.75 
and b.reviews.content : `very`

but it expressed something different and it works the same with a FLATTENED structure