purpose is allow to assign picking to users
- add field responsible on the picking that allows to select a user
- Now we assign responsible to several picking at once
- add default filter 'My Transfers' and 'Unassigned Transfers'
Related task : 1938107
closes odoo/odoo#31138
Signed-off-by: Simon Lejeune (sle) <sle@openerp.com>