Add first version of a new sidebar, including project selector.

The project selector also allows to select targets.
However, this is not yet used, since the necessary
changes are still being stabilized.

Done-with: con

src/plugins/coreplugin/modemanager.cpp

@@ -205,6 +205,11 @@ void ModeManager::addAction(Command *command, int priority, QMenu *menu)
     m_actionBar->insertAction(index, command->action(), menu);
 }
 
+void ModeManager::addProjectSelector(QAction *action)
+{
+    m_actionBar->addProjectSelector(action);
+}
+
 void ModeManager::currentTabAboutToChange(int index)
 {
     if (index >= 0) {