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/widget/projectexplorer/projectexplorer.h

@@ -26,7 +26,6 @@
 #include <QTimer>
 #include <QTreeView>
 
-#include "node/input/media/media.h"
 #include "project/project.h"
 #include "project/projectviewmodel.h"
 #include "widget/projectexplorer/projectexplorericonview.h"
@@ -58,7 +57,7 @@ public:
 
   QModelIndex get_root_index() const;
 
-  void set_root(Item* item);
+  void set_root(Folder *item);
 
   QVector<Item *> SelectedItems() const;
 
@@ -103,11 +102,6 @@ signals:
   void DoubleClickedItem(Item* item);
 
 private:
-  /**
-   * @brief Check if an item is in use anywhere and return any relevant input nodes
-   */
-  QVector<MediaInput*> GetMediaNodesUsingFootage(Footage* item);
-
   /**
    * @brief Get all the blocks that solely rely on an input node
    *