[IMP] crm_leads: default filter is 'not dead' instead if 'unassigned' and displays an info message in the crm.stage form view
            Dead leads should'nt be included in the default view since they can pollute the view over time. Instead, a filter
            for all leads (except the dead ones) is used by default. A small info message inform the user that the "dead" status
            is equivalent to setting probabilities to 0 and to fold the stage in kanban for a crm.stage.