moved timeline undoable commands to using the new NodeAddCommand

Previous iteration used some "magic code" that added clips automatically to the
timeline. This was functional but ultimately outside of the undo commands'
control meaning nodes could be infinitely added and abandoned. This makes the
add process part of the undo command which means it's all undoable as the user
would expect.

app/widget/timelinewidget/tool/pointer.cpp

@@ -30,6 +30,7 @@
 #include "config/config.h"
 #include "core.h"
 #include "node/block/gap/gap.h"
+#include "widget/nodeview/nodeviewundo.h"
 
 TimelineWidget::PointerTool::PointerTool(TimelineWidget *parent) :
   Tool(parent),
@@ -158,10 +159,6 @@ void TimelineWidget::PointerTool::MouseReleaseInternal(TimelineViewMouseEvent *e
 {
   Q_UNUSED(event)
 
-  // We create a QObject on the stack so that when we allocate objects on the heap, they aren't parent-less and will
-  // get cleaned up if they aren't re-parented by the attached NodeGraph
-  QObject block_memory_manager;
-
   QUndoCommand* command = new QUndoCommand();
 
   // Since all the ghosts will be leaving their old position in some way, we replace all of them with gaps here so the
@@ -171,9 +168,12 @@ void TimelineWidget::PointerTool::MouseReleaseInternal(TimelineViewMouseEvent *e
 
     // Replace old Block with a new Gap
     GapBlock* gap = new GapBlock();
-    gap->setParent(&block_memory_manager);
     gap->set_length(b->length());
 
+    new NodeAddCommand(static_cast<NodeGraph*>(b->parent()),
+                       gap,
+                       command);
+
     new TrackReplaceBlockCommand(parent()->GetTrackFromReference(ghost->Track()),
                                  b,
                                  gap,