Add support for add_remove on many2many widget

If a one2many is displayed with the many2many widget, the widget should support
the add_remove attribute.

review1231002

tryton/gui/window/view_form/view/form_gtk/many2many.py

@@ -146,6 +146,9 @@ class Many2Many(WidgetInterface):
         if not self.focus_out:
             return
         domain = self.field.domain_get(self.record)
+        add_remove = self.record.expr_eval(self.attrs.get('add_remove'))
+        if add_remove:
+            domain = [domain, add_remove]
         context = self.field.context_get(self.record)
         value = self.wid_text.get_text()
 
@@ -263,6 +266,9 @@ class Many2Many(WidgetInterface):
         elif index == 1:
             model = self.attrs['relation']
             domain = self.field.domain_get(self.record)
+            add_remove = self.record.expr_eval(self.attrs.get('add_remove'))
+            if add_remove:
+                domain = [domain, add_remove]
             context = self.field.context_get(self.record)
 
             screen = Screen(model, domain, context=context, mode=['form'])