[FIX] base: ambiguous @required for name of ir.actions subclasses

Column `name` is required in ir.actions, and thus
automatically required in subclasses such as `ir.actions.act_window`
and `ir.actions.act_url`, due to the specific PostgreSQL inheritance
mechanism. Mark it so in the model to make it explicit.
This does not change the database constraints, as they should already
be set though inheritance.

Closes #4861

openerp/addons/base/ir/ir_actions.py

@@ -269,7 +269,7 @@ class ir_actions_act_window(osv.osv):
         return res
 
     _columns = {
-        'name': fields.char('Action Name', translate=True),
+        'name': fields.char('Action Name', required=True, translate=True),
         'type': fields.char('Action Type', required=True),
         'view_id': fields.many2one('ir.ui.view', 'View Ref.', ondelete='set null'),
         'domain': fields.char('Domain Value',
@@ -405,7 +405,7 @@ class ir_actions_act_url(osv.osv):
     _sequence = 'ir_actions_id_seq'
     _order = 'name'
     _columns = {
-        'name': fields.char('Action Name', translate=True),
+        'name': fields.char('Action Name', required=True, translate=True),
         'type': fields.char('Action Type', required=True),
         'url': fields.text('Action URL',required=True),
         'target': fields.selection((