ZF-12505: Zend\Form\Collection does not maintain fieldset order
Collection does not maintain element order returned by POST. (It maintains data objects order, but not fieldsets order). This creates problems for cases when user can reorder fieldsets, it can foreach objects in correct order, but when fieldset is displayd after POST request (let's say in case of validation error), fieldset order is still the old one. New fieldsets are added in the end. They should be on their correct places.
(Zend framework 2 issue)