implemented external xml/shader loading for transitions as well as regular nodes

Transitions are nodes but have a few parameters that are programmatic and always
required. This lets people write external code for transitions as well.

app/node/external.h

@@ -4,6 +4,7 @@
 #include <QXmlStreamReader>
 
 #include "node.h"
+#include "metareader.h"
 
 /**
  * @brief A node generated from an external XML metadata file
@@ -29,28 +30,7 @@ public:
   virtual NodeInput* AcceleratedCodeIterativeInput() const override;
 
 private:
-  void XMLReadLanguageString(QXmlStreamReader* reader, QMap<QString, QString>* map);
-  void XMLReadEffect(QXmlStreamReader *reader);
-  void XMLReadIterations(QXmlStreamReader* reader);
-  void XMLReadParam(QXmlStreamReader* reader);
-  void XMLReadShader(QXmlStreamReader* reader, QString& destination);
-
-  static QString GetStringForCurrentLanguage(const QMap<QString, QString> *language_map);
-
-  QString xml_filename_;
-
-  QMap<QString, QString> names_;
-  QMap<QString, QString> descriptions_;
-  QMap<QString, QString> categories_;
-  QMap<QString, QMap<QString, QString> > param_names_;
-
-  QString id_;
-
-  QString frag_code_;
-  QString vert_code_;
-
-  int iterations_;
-  NodeInput* iteration_input_;
+  NodeMetaReader meta_;
 };
 
 #endif // EXTERNALNODE_H