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/widget/timelinewidget/tool/add.cpp

@@ -123,7 +123,7 @@ void AddTool::MouseRelease(TimelineViewMouseEvent *event)
                            solid,
                            command);
 
-        new NodeEdgeAddCommand(solid->output(), clip->texture_input(), command);
+        new NodeEdgeAddCommand(solid, clip->texture_input(), -1, command);
         break;
       }
       case olive::Tool::kAddableTitle:
@@ -134,7 +134,7 @@ void AddTool::MouseRelease(TimelineViewMouseEvent *event)
                            text,
                            command);
 
-        new NodeEdgeAddCommand(text->output(), clip->texture_input(), command);
+        new NodeEdgeAddCommand(text, clip->texture_input(), -1, command);
         break;
       }
       case olive::Tool::kAddableBars: