implement entire project in nodes

Project items are now represented directly in nodes opening up more versatility and possibilities. This is the first iteration of this and will be buggy. Need to test thoroughly.

app/core.h

@@ -241,7 +241,7 @@ public:
   /**
    * @brief Show a dialog to the user to rename a set of nodes
    */
-  void LabelNodes(const QVector<Node *> &nodes) const;
+  void LabelNodes(const QVector<Node *> &nodes);
 
   /**
    * @brief Create a new sequence named appropriately for the active project
@@ -488,7 +488,7 @@ private:
   /**
    * @brief Retrieves the currently most active sequence for exporting
    */
-  ViewerOutput* GetSequenceToExport();
+  Sequence* GetSequenceToExport();
 
   /**
    * @brief Internal main window object