sweeping node graph changes for new rendering pipeline

The new rendering pipeline strives to simplify the nodes themselves as much
as possible and move much of the logic to an external rendering engine. This
change removes all of the responsibilities that no longer belong to the
nodes themselves and will soon be folded into the renderer.

app/node/output/timeline/timeline.cpp

@@ -93,11 +93,8 @@ const rational &TimelineOutput::Timebase()
   return timebase_;
 }
 
-QVariant TimelineOutput::Value(NodeOutput *output, const rational &in, const rational &out)
+QVariant TimelineOutput::Value(NodeOutput *output)
 {
-  Q_UNUSED(in)
-  Q_UNUSED(out)
-
   if (output == length_output_) {
     return QVariant::fromValue(length_);
   }