various small code cleanups and improvements

Largely refactoring work to make the code somewhat nicer to work with.

app/dialog/export/export.cpp

@@ -179,7 +179,7 @@ void ExportDialog::accept()
                                         dest_height);
 
   // FIXME: Hardcoded pixel format
-  VideoRenderingParams video_render_params(dest_width, dest_height, video_tab_->frame_rate().flipped(), olive::PIX_FMT_RGBA32F, olive::kOnline);
+  VideoRenderingParams video_render_params(dest_width, dest_height, video_tab_->frame_rate().flipped(), PixelFormat::PIX_FMT_RGBA32F, RenderMode::kOnline);
 
   // FIXME: Hardcoded sample format
   AudioRenderingParams audio_render_params(audio_tab_->sample_rate_combobox()->currentData().toInt(),

app/dialog/footageproperties/footageproperties.cpp

@@ -31,10 +31,10 @@
 #include <QCheckBox>
 #include <QSpinBox>
 
+#include "core.h"
 #include "render/colormanager.h"
 #include "streamproperties/audiostreamproperties.h"
 #include "streamproperties/videostreamproperties.h"
-#include "undo/undostack.h"
 
 FootagePropertiesDialog::FootagePropertiesDialog(QWidget *parent, Footage *footage) :
   QDialog(parent),
@@ -117,7 +117,7 @@ void FootagePropertiesDialog::accept() {
     static_cast<StreamProperties*>(stacked_widget_->widget(i))->Accept(command);
   }
 
-  olive::undo_stack.pushIfHasChildren(command);
+  Core::instance()->undo_stack()->pushIfHasChildren(command);
 
   QDialog::accept();
 }

app/dialog/projectproperties/projectproperties.cpp

@@ -36,7 +36,7 @@ namespace OCIO = OCIO_NAMESPACE::v1;
 
 ProjectPropertiesDialog::ProjectPropertiesDialog(QWidget *parent) :
   QDialog(parent),
-  working_project_(olive::core.GetActiveProject())
+  working_project_(Core::instance()->GetActiveProject())
 {
   QVBoxLayout* layout = new QVBoxLayout(this);
 

app/dialog/sequence/sequence.cpp

@@ -177,7 +177,7 @@ void SequenceDialog::accept()
                                                                    audio_params,
                                                                    name_field_->text());
 
-    olive::undo_stack.push(param_command);
+    Core::instance()->undo_stack()->push(param_command);
 
   } else {
     // Set sequence values directly with no undo command

app/dialog/speedduration/speedduration.cpp

@@ -7,8 +7,8 @@
 #include <QLabel>
 #include <QVBoxLayout>
 
+#include "core.h"
 #include "common/timecodefunctions.h"
-#include "undo/undostack.h"
 #include "widget/nodeview/nodeviewundo.h"
 #include "widget/timelinewidget/undo/undo.h"
 
@@ -241,7 +241,7 @@ void SpeedDurationDialog::accept()
     }
   }
 
-  olive::undo_stack.pushIfHasChildren(command);
+  Core::instance()->undo_stack()->pushIfHasChildren(command);
 
   QDialog::accept();
 }