clarify close dialog on qtconsole

Notes that kernels not started by the qtconsole will not be affected,
and has singular message rather than 'all tabs' when only one tab
exists.

closes gh-946

IPython/frontend/qt/console/mainwindow.py

@@ -818,12 +818,16 b' class MainWindow(QtGui.QMainWindow):'
         okay = QtGui.QMessageBox.Ok
         
         if self.confirm_exit:
-            msg = "Close all tabs, stop all kernels, and Quit?"
+            if self.tab_widget.count() > 1:
+                msg = "Close all tabs, stop all kernels, and Quit?"
+            else:
+                msg = "Close console, stop kernel, and Quit?"
+            info = "Kernels not started here (e.g. notebooks) will be left alone."
             closeall = QtGui.QPushButton("&Yes, quit everything", self)
             closeall.setShortcut('Y')
             box = QtGui.QMessageBox(QtGui.QMessageBox.Question,
                                     title, msg)
-            # box.setInformativeText(info)
+            box.setInformativeText(info)
             box.addButton(cancel)
             box.addButton(closeall, QtGui.QMessageBox.YesRole)
             box.setDefaultButton(closeall)