added save functions to various classes

Each class is responsible for its own saving and loading from the XML data
in order to reduce the complexity of the save code.

app/project/item/sequence/sequence.cpp

@@ -38,6 +38,19 @@ Sequence::Sequence() :
 {
 }
 
+void Sequence::Save(QXmlStreamWriter *writer) const
+{
+  writer->writeStartElement("sequence");
+
+  writer->writeAttribute("name", name());
+
+  foreach (Node* node, nodes()) {
+    node->Save(writer);
+  }
+
+  writer->writeEndElement(); // sequence
+}
+
 void Sequence::Open(Sequence* sequence)
 {
   // FIXME: This is fairly "hardcoded" behavior and doesn't support infinite panels
@@ -62,7 +75,6 @@ void Sequence::add_default_nodes()
   Node* audio_track_output = viewer_output_->track_list(Timeline::kTrackTypeAudio)->AddTrack();
   NodeParam::ConnectEdge(video_track_output->output(), viewer_output_->texture_input());
   NodeParam::ConnectEdge(audio_track_output->output(), viewer_output_->samples_input());
-  //timeline_output_->track_list(TrackType::kTrackTypeVideo)->AddTrack();
 
   // Update the timebase on these nodes
   set_video_params(video_params_);