changed some icons and added classes for timeline view

app/widget/timelineview/timelineview.cpp

@@ -0,0 +1,16 @@
+#include "timelineview.h"
+
+TimelineView::TimelineView(QWidget *parent) :
+  QGraphicsView(parent),
+  sequence_(nullptr)
+{
+}
+
+void TimelineView::SetSequence(Sequence *s)
+{
+  scene_.clear();
+
+  sequence_ = s;
+
+  QList<Node*> sequence_nodes = sequence_->nodes();
+}