Fix bug with not preserving the original entity objects in a Collection upon validating the form
Add test case for verifying that a Collection preserves original entity objects upon form validation
Add fieldset class needed by Zend\Form\FormTest::testPreserveEntitiesBoundToCollectionAfterValidation
Merge branch 'hotfix/4095'

Close #4095
Merge pull request #4077 from sjuvonen/master

Fix Collection form element replacing bound objects with dummies upon form validation
[#4077] CS fixes

- braces
Merge branch 'hotfix/4077' into develop

Forward port #4077