Fix bug on empty headers
Fix bug of delimiter/headers not updating in admin mode
Change the __gar__ behavior: also collects None fields.
__gar__ special attribute no longer flatten uncollected data (now a list)
Update release notes
Update tests
Fix bug of None key_fields represented as "None" in CLI
Fix bug of uninitialized variable on None paths
Forbid empty delimiter when asking questions
Extend custom readers for empty delimiter