Make display rendering colours theme-aware.

* In particular this removes hard-coded checkerboard colours that don't
  look right on dark themes.

qrenderdoc/Windows/Dialogs/SettingsDialog.cpp

@@ -450,7 +450,11 @@ void SettingsDialog::on_UIStyle_currentIndexChanged(int index)
   m_Ctx.Config().UIStyle = newStyle;
 
   if(ret == QMessageBox::Yes)
+  {
     m_Ctx.Config().SetStyle();
 
+    m_Ctx.Config().SetupFormatting();
+  }
+
   m_Ctx.Config().Save();
 }