In order to have a pertinent value for the computed volume, the dimension fields
must be set on all the products.

The computed volume depends on the move state.

* If the move is done, the volume is the volume for the qty done.
* If the move is cancelled or draft waiting, the volume is the volume for the
  qty to do.
* if the move is available or partially available, the volume is the volume
  for the reserved quantity.

When the module is installed on an existing database, the volume field is only
computed for the stock moves of pickings not yet processed.
The moves in a cancelled or done picking are not updated to avoid to freeze the
database for a long time during the upgrade process if it contains a lot of
stock moves and pickings.
