PIM-1716 : remove deprecated flexible attribute form type and refactor
the product attribute form type
PIM-1716 : Refactor AddAttributeTypeRelatedFieldsSubscriber
PIM-1716 : refactor attribute option form type
PIM-1716 : refactor AttributeOptionValueType
PIM-1716 : refactor image form type
PIM-1716 : rename product value option table
PIm-1716 : refactor product create and edit form by using getParent and
form alias for product value
PIM-1716 : refactor product value type
PIM-1716 : replace FlexibleManager by ProductManager in catalog forms
PIM-1716 : replace FlexibleManager by ProductManager in mass edit action
PIM-1716 : fix a mock method naming
Merge pull request #601 from akeneo/refactor/form_attribute_type

[WIP] Refactor/form attribute type