Thumnail Management tab should update fields after delete operation

[thenadz]

This would include the thumbnails displayed (eg: if I am viewing 10 per page and delete 5, the next 5 should be appended to the existing list), the page count, the thumbnail count, and anything else that would make sense to update.

Most of these things could be part of the delete response. The thumbnails to replace deleted ones is tricky, but possible if the delete request is modified to include sort order and current page. Ideally we will still only have 1 request and 1 response for a delete action.