VK support

git-svn-id: https://plugins.svn.wordpress.org/video-thumbnails/trunk@859638 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fixed bug detecting VK IDs

git-svn-id: https://plugins.svn.wordpress.org/video-thumbnails/trunk@859790 b8457f37-d9ea-0310-8a92-e5e31aec5664