code: use macros for default node functions

Easier to maintain

app/node/block/subtitle/subtitle.cpp

@@ -31,11 +31,6 @@ SubtitleBlock::SubtitleBlock()
   AddInput(kTextIn, NodeValue::kText, InputFlags(kInputFlagNotConnectable | kInputFlagNotKeyframable));
 }
 
-Node *SubtitleBlock::copy() const
-{
-  return new SubtitleBlock();
-}
-
 QString SubtitleBlock::Name() const
 {
   return tr("Subtitle");

app/node/block/subtitle/subtitle.h

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