code: use macros for default node functions

Easier to maintain

app/node/block/gap/gap.cpp

@@ -26,11 +26,6 @@ GapBlock::GapBlock()
 {
 }
 
-Node *GapBlock::copy() const
-{
-  return new GapBlock();
-}
-
 QString GapBlock::Name() const
 {
   return tr("Gap");

app/node/block/gap/gap.h

@@ -34,9 +34,7 @@ class GapBlock : public Block
 public:
   GapBlock();
 
-  NODE_DEFAULT_DESTRUCTOR(GapBlock)
-
-  virtual Node * copy() const override;
+  NODE_DEFAULT_FUNCTIONS(GapBlock)
 
   virtual QString Name() const override;
   virtual QString id() const override;