Revert "Fix: IEnumerable.Clone/ChangeTrackingCollection.GetChanges don't preserve object references correctly"

This reverts commit 914434be6c22acf44c94ffaff8bd7133bc332ec0.
Revert "Extend the Clone_Of_ChangeTrackingCollection_Should_Create_Deep_Copy unit test to demonstrate that the IEnumerable.Clone extension method doesn't preserve object references correctly"

This reverts commit be4662bf90e31919a9dd1515d8a3967fac9e8c53.
Fixed bug in ApplyChanges with modified parent and multiple added children.
DONT PUSH: my local connection string
Merge remote-tracking branch 'remotes/az-codepex/DbContextExtensions.OSpace' into MY-develop
Extend the Clone_Of_ChangeTrackingCollection_Should_Create_Deep_Copy unit test to demonstrate that the IEnumerable.Clone extension method may lead to an unnecessary copy of an entity
Extend the GetChanges_On_Unchanged_Order_With_Details_Should_Return_Marked_Children unit test to demonstrate that the ChangeTrackingCollection.GetChanges method may lead to an unnecessary copy of an entity
Fix: IEnumerable.Clone/ChangeTrackingCollection.GetChanges may lead to an unnecessary copy of an entity