[FIX] project: duplicate project must copy followers

Since duplicating a project copies the project
tasks, with the followers, the project followers must
remain as well.

This is done in the already overriden method
`copy` instead of simply adding `copy=True`
on the according one2many field, since this field
is defined on the inherited model
`mail.thread`, and to add `copy=True`, in the old api,
we would have to re-define the `message_follower_ids`
field within the `project.project`
model completely, making sure to copy all properties

opw-680313

addons/project/project.py

@@ -255,6 +255,7 @@ class project(osv.osv):
         proj = self.browse(cr, uid, id, context=context)
         if not default.get('name'):
             default.update(name=_("%s (copy)") % (proj.name))
+        default['message_follower_ids'] = [(6, 0, proj.message_follower_ids.ids)]
         res = super(project, self).copy(cr, uid, id, default, context)
         self.map_tasks(cr, uid, id, res, context=context)
         return res