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/task/precache/precachetask.cpp

@@ -34,7 +34,7 @@ PreCacheTask::PreCacheTask(VideoStream *footage, Sequence* sequence) :
   video_node_ = new MediaInput();
   video_node_->SetStream(footage);
 
-  NodeParam::ConnectEdge(video_node_->output(), viewer()->texture_input());
+  Node::ConnectEdge(video_node_, viewer()->texture_input());
 
   SetTitle(tr("Pre-caching %1:%2").arg(footage->footage()->filename(),
                                        QString::number(footage->index())));