Configure video bundle to use the same formatters as image bundle for media_preview and media_large view modes

HEAD contains this code in media_enable():

$view_mode_settings['image']['media_preview'] = 'styles_file_square_thumbnail';
$view_mode_settings['image']['media_large'] = 'styles_file_large';
...
$view_mode_settings['video']['media_large'] = 'styles_file_large';

There are two things wrong with this:
1) It makes sense for video to use the same formatter as images for 'media_preview' as well as for 'media_large'. The whole point of the Styles module is that at this level, images and video should be treated the same way, and whatever differences we need in how to render video differently from images should be encapsulated within Styles settings.
2) Whenever $view_mode_settings['video']['media_large'] = 'styles_file_large'; was added, it was done so without a corresponding update function.

This patch addresses these two problems.