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
[DDC-1398] Extra-lazy get for indexed associations

If an association is EXTRA_LAZY and has an indexBy, then
you can call get() without loading the entire collection.
Return NULL for non-existent keys

The load() function already returns just one entity or NULL, so
the current() is not needed and the result can be returned directly.
Test actual data returned by get()
Get rid of variable
Use find() if the indexBy field is the identifier
No need to lookup metadata
Extra test for indexBy identifier versus indexBy other fields
Merge pull request #706 from sandermarechal/extra-lazy-get

[DDC-1398] Extra-lazy get for indexed associations
ANSI compliant quote strategy
Fix DDC-2519
Merge pull request #705 from FabioBatSilva/DDC-2519

[DDC-2519] Partial association identifier
Merge pull request #702 from FabioBatSilva/DDC-2459

[DDC-2459]ANSI compliant quote strategy
Dont allow failures in 5.5 anymore
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'