OutputPane: Add an id() for the settings

It was using the displayName for the key in the settings (visibility and
shortcut), which is annoying when changing the language.

Change-Id: Iffa784347c59389599c90f468dcba15834599c39
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>

src/plugins/coreplugin/messageoutputwindow.cpp

@@ -20,6 +20,7 @@ const char zoomSettingsKey[] = "Core/MessageOutput/Zoom";
 
 MessageOutputWindow::MessageOutputWindow()
 {
+    setId("GeneralMessages");
     setDisplayName(Tr::tr("General Messages"));
     m_widget = new OutputWindow(Context(Constants::C_GENERAL_OUTPUT_PANE), zoomSettingsKey);
     m_widget->setReadOnly(true);