* Adds a `describe` option to the workflow controller to support inline caption editing.
* For images, descriptions are mapped to the `caption` attribute.
* For other media items, descriptions are mapped to the `title` attribute.
* Descriptions are saved when the textarea's `change` event fires (i.e. when the textarea is blurred).
fixes#21807, see #21390.
git-svn-id: http://core.svn.wordpress.org/trunk@22173 1a063a9b-81f0-0310-95a4-ce76da25c4cd