Fixed JS "changed" trigger for metabox elements

git-svn-id: https://plugins.svn.wordpress.org/attached-posts/trunk@787516 b8457f37-d9ea-0310-8a92-e5e31aec5664
Added "disabled" class for disabled file upload fields in backend

git-svn-id: https://plugins.svn.wordpress.org/attached-posts/trunk@791227 b8457f37-d9ea-0310-8a92-e5e31aec5664