Add hidden field ordering for postgresql

In postgresql environment, when some hidden fields are used in orderBy clause,
they're not property added because $rsm->scalarMappings don't have information about them.
Revert "Add hidden field ordering for postgresql"

This reverts commit 3e8796f78188e193aac7386b38b7e17da3df5718.
Add test for postgresql hidden scalar sorting
Fixed postgresql hidden scalar sort
Merge pull request #640 from denkiryokuhatsuden/patch-1

[Paginator]Add hidden field ordering for postgresql
[DDC-2350] Eager Collections are not marked as initialized, leading to multiple queries being executed.
Merge branch 'DDC-2530'
add coveralls