use strings to connect nodes

This makes the node system somewhat more high-level with the intent of making
working with them far more flexible and stable. By making the architecture more
abstracted, it becomes far less rigid which should allow us to do even more
with it and make it much less crash prone.

app/node/keyframe.h

@@ -26,11 +26,11 @@
 #include <QVariant>
 
 #include "common/rational.h"
+#include "node/param.h"
 
 namespace olive {
 
-class NodeInput;
-class NodeInputImmediate;
+class Node;
 
 /**
  * @brief A point of data to be used at a certain time and interpolated with other data
@@ -61,14 +61,23 @@ public:
   /**
    * @brief NodeKeyframe Constructor
    */
-  NodeKeyframe(const rational& time, const QVariant& value, const Type& type, const int& track, int element, QObject* parent = nullptr);
+  NodeKeyframe(const rational& time, const QVariant& value, Type type, int track, int element, const QString& input, QObject* parent = nullptr);
 
   virtual ~NodeKeyframe() override;
 
   NodeKeyframe* copy(int element, QObject* parent = nullptr) const;
   NodeKeyframe* copy(QObject* parent = nullptr) const;
 
-  NodeInput* parent() const;
+  Node* parent() const;
+  const QString& input() const
+  {
+    return input_;
+  }
+
+  NodeKeyframeTrackReference key_track_ref() const
+  {
+    return NodeKeyframeTrackReference(NodeInput(parent(), input(), element()), track());
+  }
 
   /**
    * @brief The time this keyframe is set at
@@ -194,6 +203,8 @@ private:
 
   QPointF bezier_control_out_;
 
+  QString input_;
+
   int track_;
 
   int element_;