Bugfix in ::Generic::List :
- small refactor of methods to avoid naming conflicts with list properties. This caused weird issues if library wasn't manually reloaded after startup.
Bugfix in ::Generic::Form :
- let edit_data and new_data methods return object_id instead of item_id, because item_id is not a real field of acs_objects and this causes issues when enabling category mapping.
- move transaction enclosing from edit_data and new_data methods definition to the final form declaration, so category mapping code will be in the transaction too
