PIM-2904: Avoid to delete or update the default user group
PIM-2904: Add the default to a user during its creation
PIM-2904: Remove the "All" group from the list in the user edit form
PIM-2904: Extract QB in repositories to clean user form
PIM-2904: Fix Behat scenarios
Merge pull request #1292 from akeneo/PIM-2904b

PIM-2904: Use a user group 'system' named 'All users'