Expose a clear method from the timeline

src/GUI/Timeline.cpp

@@ -110,6 +110,12 @@ void Timeline::changeEvent( QEvent *e )
     }
 }
 
+void Timeline::clear()
+{
+    // The main workflow will ask the GUI to clear itself.
+    m_mainWorkflow->clear();
+}
+
 void Timeline::changeZoom( int factor )
 {
     m_tracksRuler->setPixelPerMark( factor );

src/GUI/Timeline.h

@@ -46,6 +46,7 @@ public:
     static Timeline*    getInstance() { return m_instance; }
 
 public slots:
+    void clear();
     void changeZoom( int factor );
     void setDuration( int duration );
     void setTool( ToolButtons button );