rewrote renderers where necessary for new node structure

Largely conforming renderers to new NodeValue system. Code seems a lot cleaner
this way which is a nice advantage. Likely non-functional as this won't
compile just yet and still needs probably another day or two of testing to get
it back to where it was before.

app/render/backend/videorenderworker.h

@@ -16,12 +16,10 @@ public:
   void SetParameters(const VideoRenderingParams& video_params);
 
 public slots:
-  virtual QVariant RenderAsSibling(NodeDependency dep) override;
-
   void Download(NodeDependency dep, QByteArray hash, QVariant texture, QString filename);
 
 signals:
-  void CompletedFrame(NodeDependency path, QByteArray hash, QVariant value);
+  void CompletedFrame(NodeDependency path, QByteArray hash, NodeValueTable value);
 
   void CompletedDownload(NodeDependency path, QByteArray hash);
 
@@ -40,10 +38,12 @@ protected:
 
   virtual void TextureToBuffer(const QVariant& texture, QByteArray& buffer) = 0;
 
-  virtual void RenderInternal(const NodeDependency& path) override;
+  virtual NodeValueTable RenderInternal(const NodeDependency& path) override;
 
   virtual FramePtr RetrieveFromDecoder(DecoderPtr decoder, const TimeRange& range) override;
 
+  virtual NodeValueTable RenderBlock(NodeOutput *output, const TimeRange& range) override;
+
 private:
   void ProcessNode();