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/dialog/sequence/sequence.cpp

@@ -102,24 +102,17 @@ void SequenceDialog::accept()
     return;
   }
 
-  // Get the rational at the combobox's index (which will be correct provided AddFrameRate() was used at all time)
-  rational video_time_base = parameter_tab_->GetSelectedVideoFrameRate().flipped();
-
-  // Get the rational at the combobox's index (which will be correct provided AddFrameRate() was used at all time)
-  int audio_sample_rate = parameter_tab_->GetSelectedAudioSampleRate();
-
-  // Get the audio channel layout value
-  uint64_t channels = parameter_tab_->GetSelectedAudioChannelLayout();
-
   // Generate video and audio parameter structs from data
   VideoParams video_params = VideoParams(parameter_tab_->GetSelectedVideoWidth(),
                                          parameter_tab_->GetSelectedVideoHeight(),
-                                         video_time_base,
+                                         parameter_tab_->GetSelectedVideoFrameRate().flipped(),
                                          parameter_tab_->GetSelectedPreviewFormat(),
+                                         parameter_tab_->GetSelectedVideoPixelAspect(),
+                                         parameter_tab_->GetSelectedVideoInterlacingMode(),
                                          parameter_tab_->GetSelectedPreviewResolution());
 
-  AudioParams audio_params = AudioParams(audio_sample_rate,
-                                         channels,
+  AudioParams audio_params = AudioParams(parameter_tab_->GetSelectedAudioSampleRate(),
+                                         parameter_tab_->GetSelectedAudioChannelLayout(),
                                          SampleFormat::kInternalFormat);
 
   if (make_undoable_) {