plot: Add sample output interface

plot.cpp

@@ -19,11 +19,21 @@
 
 #include "plot.h"
 
+Plot::Plot(std::shared_ptr<AbstractSampleSource> src) : sampleSource(src)
+{
+
+}
+
 bool Plot::mouseEvent(QEvent::Type type, QMouseEvent event)
 {
 
 }
 
+std::shared_ptr<AbstractSampleSource> Plot::output()
+{
+	return sampleSource;
+}
+
 void Plot::paintBack(QPainter &painter, QRect &rect, range_t<off_t> sampleRange)
 {
     painter.save();