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/opengl/openglworker.cpp

@@ -83,7 +83,7 @@ void OpenGLWorker::ParametersChangedEvent()
   }
 }
 
-QVariant OpenGLWorker::RunNodeAccelerated(NodeOutput *out)
+NodeValueTable OpenGLWorker::RunNodeAccelerated(NodeOutput *out)
 {
   OpenGLShaderPtr shader = shader_cache_->GetShader(out);
   Node* node = out->parentNode();