Do not remove the Keep button completely, keep around for backward compatibility

In order to allow activities keeping their backward compatibility
we keep the Keep button around but do not add it to the toolbar. This
fixes activities that either remove or hide the Keep button or
alter it in any other way. The Keep button is deprecated and we
discourage the usage.

Signed-off-by: Simon Schampijer <simon@laptop.org>
Reviewed-by: Gonzalo Odiard <gonzalo@laptop.org>

src/sugar/activity/widgets.py

@@ -265,6 +265,9 @@ class ActivityToolbar(gtk.Toolbar):
         self.share.show()
         self.insert(self.share, -1)
 
+        # DEPRECATED
+        self.keep = KeepButton(activity)
+
         self.stop = StopButton(activity)
         self.insert(self.stop, -1)
         self.stop.show()