removed all dependence on NodeOutputs

If Nodes only have the one output, we don't need to do so much differentiation
between them. Previous iteration used outputs as like a distinct function
within a Node (e.g. length output would return one result, buffer output would
produce a different result - each run different code to produce their results).
Now in this iteration, it's more accurate to say a Node is just one function
(which seems more appropriate for a node system anyway).

app/node/blend/blend.h

@@ -34,14 +34,13 @@ public:
 
   NodeInput* blend_input() const;
 
-  NodeOutput* texture_output() const;
+  virtual void Retranslate() override;
 
 private:
   NodeInput* base_input_;
 
   NodeInput* blend_input_;
 
-  NodeOutput* texture_output_;
 };
 
 #endif // BLEND_H