Adds a button to clone the BB track pattern

Adds a button on the BBEditor that clones the current BB track pattern, but without also cloning the song editor TCOs. That can be useful when an user is editing drumlines and wants to make a section with a slight variation for example.

include/BBEditor.h

@@ -86,6 +86,7 @@ public slots:
 	void removeSteps();
 	void addSampleTrack();
 	void addAutomationTrack();
+	void cloneBBTrackPattern();
 
 protected slots:
 	void dropEvent(QDropEvent * de ) override;