Change the current implementation (suggested by Denis Roussel from
ACSONE):

- A new parameter on stock picking types : 'Product Change Location'
  (with a little help).
- With this, go to the dashboard, create a picking with that type.
- Add a button on the picking form which is visible with that type that
  fill in the picking as now
- Nice to have: add a magic button on locations that with context
  creates a new picking of that type with the origin location already
  filled in.