various: implement sequence pixel aspect ratios and interlacing settings

Implements the following:
- Sequences have pixel aspect ratios that work in tandem with footage PARs
  to render footage correctly. Viewer and export also acknowledge PARs
- Sequences can have interlacing settings. This doesn't do anything yet,
  eventually the renderer will need to interlace/deinterlace/reinterlace
  appropriately in order to conform all the footage to the sequence. Export
  acknowledges interlacing, but this only affects metadata, not the image.

app/render/backend/renderworker.cpp

@@ -127,6 +127,8 @@ void RenderWorker::RenderFrame(RenderTicketPtr ticket, ViewerOutput* viewer, con
                                       video_params_.height(),
                                       video_params_.time_base(),
                                       output_format,
+                                      video_params_.pixel_aspect_ratio(),
+                                      video_params_.interlacing(),
                                       video_params_.divider()));
   frame->set_timestamp(time);
   frame->allocate();
@@ -295,6 +297,8 @@ QVariant RenderWorker::ProcessFrameGeneration(const Node* node, const GenerateJo
                                       video_params_.height(),
                                       video_params_.time_base(),
                                       output_fmt,
+                                      video_params_.pixel_aspect_ratio(),
+                                      video_params_.interlacing(),
                                       video_params_.divider()));
   frame->allocate();
 
@@ -316,6 +320,8 @@ QVariant RenderWorker::GetCachedFrame(const Node* node, const rational& time)
                                       f->height() * video_params_.divider(),
                                       f->video_params().time_base(),
                                       f->video_params().format(),
+                                      f->video_params().pixel_aspect_ratio(),
+                                      f->video_params().interlacing(),
                                       video_params_.divider()));
 
       return CachedFrameToTexture(f);