Launchpad automatic translations update.
[FIX] orm: do not drop low level columns (aka 'magic columns') when deleting ir.model.fields
[MERGE] [FIX] models: do not drop low level columns (aka 'magic columns') when deleting ir.model.fields

Without this fix, uninstalling modules using id, create_date,... in their field declaration while inheriting from existing module would drop these columns