TrackArtist needs only Track, not WaveTrack...

... and clean up some other things

src/TrackArtist.cpp

@@ -45,17 +45,14 @@ audio tracks.
 
 #include "AColor.h"
 #include "AllThemeResources.h"
-#include "Prefs.h"
 #include "prefs/GUIPrefs.h"
+#include "Track.h"
 #include "TrackPanelDrawingContext.h"
 #include "ViewInfo.h"
-#include "WaveTrack.h"
 
 #include "prefs/GUISettings.h"
 #include "prefs/TracksPrefs.h"
 
-#include <wx/dc.h>
-
 TrackArtist::TrackArtist( TrackPanel *parent_ )
    : parent( parent_ )
 {
@@ -237,12 +234,6 @@ void TrackArt::DrawNegativeOffsetTrackArrows(
 }
 
 
-// Headers needed only for experimental drawing below
-//#include "tracks/ui/TimeShiftHandle.h"
-//#include "tracks/playabletrack/wavetrack/ui/CutlineHandle.h"
-namespace {
-}
-
 #ifdef __GNUC__
 #define CONST
 #else