began new infrastructure

Yep, this is another one of my "famous" sweeping rewrites. Expect things to break.

Goals for this are:
- Greatly simplify node connections (particularly with arrays) so the code requires less maintenance/is more stable
- Redesign node structure to address issues where UI would stall for lengthy periods of time
- Less reliance on shared ptrs/greater reliance on QObject system for inheritance/memory management
- General code cleanup and improvements

app/node/inputdragger.h

@@ -32,7 +32,7 @@ public:
 
   bool IsStarted() const;
 
-  void Start(NodeInput* input, const rational& time, int track);
+  void Start(NodeInput* input, const rational& time, int track, int element = -1);
 
   void Drag(QVariant value);
 
@@ -45,11 +45,13 @@ private:
 
   rational time_;
 
+  int element_;
+
   QVariant start_value_;
 
   QVariant end_value_;
 
-  NodeKeyframePtr dragging_key_;
+  NodeKeyframe* dragging_key_;
 
   bool drag_created_key_;