code: use macros for default node functions

Easier to maintain

app/node/generator/solid/solid.cpp

@@ -34,11 +34,6 @@ SolidGenerator::SolidGenerator()
   AddInput(kColorInput, NodeValue::kColor, QVariant::fromValue(Color(1.0f, 0.0f, 0.0f, 1.0f)));
 }
 
-Node *SolidGenerator::copy() const
-{
-  return new SolidGenerator();
-}
-
 QString SolidGenerator::Name() const
 {
   return tr("Solid");

app/node/generator/solid/solid.h

@@ -31,9 +31,7 @@ class SolidGenerator : public Node
 public:
   SolidGenerator();
 
-  NODE_DEFAULT_DESTRUCTOR(SolidGenerator)
-
-  virtual Node* copy() const override;
+  NODE_DEFAULT_FUNCTIONS(SolidGenerator)
 
   virtual QString Name() const override;
   virtual QString id() const override;