Help: Implement a real external help window

With this patch it is just used with the context help "always show in
external window" option.

Change-Id: I4bc6ba8e0e241500f6970d4cb72f66ba02075ef5
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>

src/plugins/help/generalsettingspage.cpp

@@ -185,8 +185,6 @@ void GeneralSettingsPage::apply()
         settings->beginGroup(QLatin1String(Help::Constants::ID_MODE_HELP));
         settings->setValue(QLatin1String("ContextHelpOption"), helpOption);
         settings->endGroup();
-
-        emit contextHelpOptionChanged();
     }
 
     const bool close = m_ui->m_returnOnClose->isChecked();