implemented new block system

Fixes recurring design issue that the Blocks were a frequent exception to the
DAG concept. The Blocks connecting to each others inputs/outputs while not
necessarily being "dependent" on each other to produce an image continually
causes issues while trying to create a rendering code path. This redesign
should provide a more "directed" approach to the directed acyclic graph.

app/widget/timelinewidget/timelinewidget.cpp

@@ -276,7 +276,7 @@ void TimelineWidget::GoToNextCut()
   int64_t closest_cut = INT64_MAX;
 
   foreach (TrackOutput* track, timeline_node_->Tracks()) {
-    int64_t this_track_closest_cut = olive::time_to_timestamp(track->in(), timebase());
+    int64_t this_track_closest_cut = olive::time_to_timestamp(track->track_length(), timebase());
 
     if (this_track_closest_cut <= playhead_) {
       this_track_closest_cut = INT64_MAX;
@@ -592,7 +592,7 @@ void TimelineWidget::AddBlock(Block *block, TrackReference track)
     connect(block, SIGNAL(Refreshed()), this, SLOT(BlockChanged()));
     break;
   }
-  case Block::kEnd:
+  case Block::kTrack:
     // Do nothing
     break;
   }