[Plugin: Thumbnails for Backend] remove warning when WP_DEBUG is active

Hi Giorgio, I’m still enjoying this great plugin.

I would like to suggest a very minor edit for the next version to prevent the following alert notice from appearing in admin when WP_DEBUG is set to true:

Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. in /home/sites/numeeja.com/public_html/wp-includes/functions.php on line 3551

line 179 changed from

add_options_page('Thumbnails for Backend', 'Thumbnails for Backend', 8, basename(__FILE__), array(&$this, 'admin_page') );

to

add_options_page('Thumbnails for Backend', 'Thumbnails for Backend', 'edit_posts', basename(__FILE__), array(&$this, 'admin_page') );

https://www.ads-software.com/extend/plugins/thumbnailsforbackend/