* Attachments now go through post.php, edit_post(), the like, and have show_ui set to true.
* Taxonomies attached to the media library now appear in the admin menu (if show_ui).
* Editing, cropping, uploading, etc. is still very rough, but mostly functional.
API-wise:
* New function: get_taxonomies_for_attachments(). Like get_taxonomies(), for taxonomies specifically registered against attachments.
* Brings taxonomy support from the posts list table to the media list table. Expect them to converge soon.
* wp_insert_attachment() now handles taxonomies like wp_insert_post(). Also expect them to converge soon.
* New edit_form_after_title hook.
props helenyhou, ocean90. see #21391.
git-svn-id: https://develop.svn.wordpress.org/trunk@21948 602fd350-edb4-49c9-b593-d223f7449a82