[IMP] Barcode interface and transfer wizard in picking form instead

Pack operations will not appear in a transfer wizard or bar code interface anymore, but
in the picking form itself.  Some wizards are still needed however to ask whether a
backorder needs to be created and whether we need to do an immediate transfer

The biggest change in the model is in the picking where the locations of the picking
are not a related anymore, but need to be set. That is why the tests need to be changed.
This allows also to have pickings without moves initially and just move one pack e.g.
Locations won't be visible on stock moves in a picking either.  (as they should be those of the picking)

In order to avoid confusion, the pack operations are created immediately when stock is reserved and we
are not waiting until the wizard or the bar code interface is launched anymore.

The recompute button previously in the barcode interface will only appear when the reservation changed
and the user indicated in the pack operations that something was moved already.  Otherwise it will
recompute the pack operations.  That way the reservation on the stock moves, is reflected by the pack operations.

Return pickings are not confirmed automatically when confirming the return wizard.
That should make it possible to choose another location for the return.  (Don't return in output e.g.)

Barcode scanning is not in this commit.