Tested with WP 4.1, added mime type filter, fixed minor bugs

git-svn-id: https://plugins.svn.wordpress.org/quick-featured-images/trunk@1051163 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated language files

git-svn-id: https://plugins.svn.wordpress.org/quick-featured-images/trunk@1051165 b8457f37-d9ea-0310-8a92-e5e31aec5664