reversal/extourne moves
This is a placeholder for the reversal wizard as discussed on the forum.
In some countries, such as France, cancellation of a validated entry
may only be done by a reversal entry.
In addition, 'extourne' or 'storno' moves for adjusting entries use a
similar (even same) mechanism, but forcibly in a future period,
typically the first day in the next fiscal year.
It should be possible to disactivate cancellation in favour of reversal
as a policy, potentially even enforced (e.g. in account_fr)