Sample tracks: Show the file name of the loaded file in the label

Show the file name without the full path in the text label for sample
tracks. Show the file name with the full path in the tool tip.

src/tracks/SampleTrack.cpp

@@ -25,6 +25,7 @@
 #include "SampleTrack.h"
 
 #include <QDropEvent>
+#include <QFileInfo>
 #include <QMenu>
 #include <QLayout>
 #include <QMdiArea>
@@ -502,6 +503,10 @@ void SampleTCOView::paintEvent( QPaintEvent * pe )
 			qMax( static_cast<int>( m_tco->sampleLength() * ppt / ticksPerTact ), 1 ), rect().bottom() - 2 * spacing );
 	m_tco->m_sampleBuffer->visualize( p, r, pe->rect() );
 
+	QFileInfo fileInfo(m_tco->m_sampleBuffer->audioFile());
+	QString filename = fileInfo.fileName();
+	paintTextLabel(filename, p);
+
 	// disable antialiasing for borders, since its not needed
 	p.setRenderHint( QPainter::Antialiasing, false );