moved several files around

Mostly moved classes that became node derivatives into the node/ folder.

app/node/output/viewer/viewer.cpp

@@ -57,14 +57,6 @@ ViewerOutput::ViewerOutput(bool create_default_streams) :
   }
 }
 
-ViewerOutput::~ViewerOutput()
-{
-  // Should prevent traversing graph unnecessarily
-  BeginOperation();
-  DisconnectAll();
-  EndOperation();
-}
-
 Node *ViewerOutput::copy() const
 {
   return new ViewerOutput();

app/node/output/viewer/viewer.h

@@ -45,7 +45,8 @@ class ViewerOutput : public Node
   Q_OBJECT
 public:
   ViewerOutput(bool create_default_streams = true);
-  virtual ~ViewerOutput() override;
+
+  NODE_DEFAULT_DESTRUCTOR(ViewerOutput)
 
   virtual Node* copy() const override;