Advanced settings and custom theme options aren't exportable

To reproduce:

1. Create a view that uses a Views Slideshow Galleria display.
2. Under Format, click Settings, then Galleria Settings, then Custom Theme Options, and enter some text.
3. Close the window, save the view, click export.
4. Search for the text you entered in step 2.

I ran into this while using Features with a custom Galleria theme. The settings don't get exported, and are therefore destroyed on drush features-revert.

The workaround is to manually add the relevant lines to the views_default.inc file:

  $handler->display->display_options['style_options']['views_slideshow_galleria']['custom_theme_options'] = array(
    'custom_theme' => 'mytheme',
    'custom_theme_path' => 'path/to/galleria.mytheme.js',
    );