node: added qstringliterals to node IDs

Minor code optimization.

app/node/output/track/track.cpp

@@ -75,7 +75,7 @@ QString TrackOutput::Name() const
 
 QString TrackOutput::id() const
 {
-  return "org.olivevideoeditor.Olive.track";
+  return QStringLiteral("org.olivevideoeditor.Olive.track");
 }
 
 QString TrackOutput::Category() const

app/node/output/track/tracklist.cpp

@@ -111,7 +111,7 @@ TrackOutput* TrackList::AddTrack()
     if (last_track && last_track->output()->IsConnected()) {
       foreach (NodeEdgePtr edge, last_track->output()->edges()) {
         if (!track_input_->ContainsSubParameter(edge->input())) {
-          Node* blend = NodeFactory::CreateFromID("org.olivevideoeditor.Olive.alphaoverblend");
+          Node* blend = NodeFactory::CreateFromID(QStringLiteral("org.olivevideoeditor.Olive.alphaoverblend"));
           GetParentGraph()->AddNode(blend);
 
           NodeParam::ConnectEdge(track->output(), static_cast<NodeInput*>(blend->GetParameterWithID("blend_in")));

app/node/output/viewer/viewer.cpp

@@ -67,7 +67,7 @@ QString ViewerOutput::Name() const
 
 QString ViewerOutput::id() const
 {
-  return "org.olivevideoeditor.Olive.vieweroutput";
+  return QStringLiteral("org.olivevideoeditor.Olive.vieweroutput");
 }
 
 QString ViewerOutput::Category() const