Reorder statements so the order is better suitable for batch operations

[schauder]

For an Aggregate Root A with a collections of B entities which in turn has a collection of C entities, insert operations are are structured like this:

1. insert A
2. insert 1. B
3. insert 1. C of 1.B
4. insert 2. C of 1.B
   ...
5. insert 1. B
6. insert 1. C of 2.B
7. insert 2. C of 2.B
   ...

This is not well suited for batch operations.
For those we should execute the statements in the following order:

1. insert A
2. insert 1. B
3. insert 1. B
   ...
4. insert 1. C of 1.B
5. insert 2. C of 1.B
6. insert 1. C of 2.B
7. insert 2. C of 2.B
   ...

See also #537

[ctailor2]

Insert statements for entities with nested collections already appear to be ordered as desired. See this passing test I added on a branch to verify that this is the case.

[schauder]

Thanks.