moved sequence params into node graph too

Reduces code by reusing more of the existing node infrastructure
to synchronize sequence parameters the render backend.

app/task/project/save/save.cpp

@@ -46,12 +46,14 @@ bool ProjectSaveTask::Run()
     QXmlStreamWriter writer(&project_file);
     writer.setAutoFormatting(true);
 
-    // Version is stored in YYMMDD from whenever the project format was last changed
-    // Allows easy integer math for checking project versions.
-    writer.writeStartDocument(QString::number(Core::kProjectVersion));
+    writer.writeStartDocument();
 
     writer.writeStartElement("olive");
 
+    // Version is stored in YYMMDD from whenever the project format was last changed
+    // Allows easy integer math for checking project versions.
+    writer.writeTextElement(QStringLiteral("version"), QString::number(Core::kProjectVersion));
+
     writer.writeTextElement("url", project_->filename());
 
     writer.writeStartElement(QStringLiteral("project"));