Modes: Do the mode switching again like it used to be

It's more complicated then expected, to be detangled another day

src/plugins/welcome/welcomeplugin.cpp

@@ -76,6 +76,7 @@ bool WelcomePlugin::initialize(const QStringList & /* arguments */, QString * /*
 void WelcomePlugin::extensionsInitialized()
 {
     m_welcomeMode->initPlugins();
+    Core::ModeManager::instance()->activateMode(m_welcomeMode->id());
 }
 
 Q_EXPORT_PLUGIN(WelcomePlugin)