Pref: - add require-reboot capability to PreferencePage.

- Implement this require-reboot in wb pref page

src/Gui/ApplicationPy.cpp

@@ -1377,6 +1377,8 @@ PyObject* Application::sShowPreferences(PyObject * /*self*/, PyObject *args)
     wc.restoreCursor();
     cDlg.exec();
     wc.setWaitCursor();
+    cDlg.isRebootRequired(); //The user may have applied first, then clicked the cancel button so it's not in the if(cDlg.exec())
+    wc.setWaitCursor();
 
     Py_Return;
 }