BS-7901 & BS-6926

- add changes in gmfmap and regenerated gmfgen to initialize the GroupIterator with empty name when created
- Ra-add case of groupiterator in EngineExpressionUtil and set correct type to output for the form.xml exported file
- Correct default validation of the GroupIterator name : the name can be empty if the iterator is not used in the Group
- Fix a validation interface (when validation of a name that is empty, it shows the name of the parent)