implement entire project in nodes

Project items are now represented directly in nodes opening up more versatility and possibilities. This is the first iteration of this and will be buggy. Need to test thoroughly.

app/task/render/render.cpp

@@ -25,7 +25,7 @@
 
 namespace olive {
 
-RenderTask::RenderTask(ViewerOutput* viewer, const VideoParams &vparams, const AudioParams &aparams) :
+RenderTask::RenderTask(Sequence* viewer, const VideoParams &vparams, const AudioParams &aparams) :
   viewer_(viewer),
   video_params_(vparams),
   audio_params_(aparams),

app/task/render/render.h

@@ -35,7 +35,7 @@ class RenderTask : public Task
 {
   Q_OBJECT
 public:
-  RenderTask(ViewerOutput* viewer, const VideoParams &vparams, const AudioParams &aparams);
+  RenderTask(Sequence* viewer, const VideoParams &vparams, const AudioParams &aparams);
 
   virtual ~RenderTask() override;
 
@@ -53,7 +53,7 @@ protected:
 
   virtual void AudioDownloaded(const TimeRange& range, SampleBufferPtr samples, qint64 job_time) = 0;
 
-  ViewerOutput* viewer() const
+  Sequence* viewer() const
   {
     return viewer_;
   }
@@ -85,7 +85,7 @@ private:
 
   void IncrementRunningTickets();
 
-  ViewerOutput* viewer_;
+  Sequence* viewer_;
 
   VideoParams video_params_;