Initiliaze input type in gmfmap

or Engine side, there is missing migration and there are test sto
rewrite but at least it will compile after Web update

initialize available values with correct name for Empty List groovy
script

- 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)

- Add class GroupIterator
- Add initialization of groupIterator in existing/new group
- Set className of iterator to Object
- Changes on the Studio UI
-- add validation on iterator name and remove the one on className
-- add iterator in Initial Value expression viewer for widgets in Group
-- Group in Form should not havea access to iterator and Group in Group should have access => does not work yet.

- Add Migration on GroupIterator

CLONE - multiple value widget with empty_list generates an error at
runtime

[6.0.4] Checkbox list widget default types suggested are String instead
of List or map

Revert "BS-1774 [6.0.4] Checkbox list widget default types suggested are String instead of List or map"

This reverts commit 2e7aa89e.

[6.0.4] Checkbox list widget default types suggested are String instead
of List or map

Conflicts:
	bundles/plugins/org.bonitasoft.studio-models/form/form.gmfgen