Update services to properly process repeating objects in a collection/object

[elrayle]

In collection/add_object_spec and object/add_object_spec...

it 'should allow objects to repeat' do
  Hydra::PCDM::AddObjectToCollection.call( subject, object1 )
  Hydra::PCDM::AddObjectToCollection.call( subject, object2 )
  Hydra::PCDM::AddObjectToCollection.call( subject, object1 )
  subject.save
  expect( Hydra::PCDM::GetObjectsFromCollection.call( subject.reload ) ).to eq [object1,object2,object1]
end

This test fails with Get returning [object1,object2].

NOTE: This test needs to be updated to save after Add and reload before Get. Otherwise, the problem is masked.

It could be that Add and Get need to be updated to process repeating objects. The other possibility is that something is happening at the ActiveFedora level.

[elrayle]

See related... #105