Cleanup audio/video shortcodes in the media modal:

* On the controller's `update`, `replace`, and `close` events, call `detach()` on the frame
* Cleanup the HTML ouput of the Underscore templates.
* Move some logic from the Underscore template to the `VideoDetails` view class.

See #27016.


Built from https://develop.svn.wordpress.org/trunk@27440


git-svn-id: http://core.svn.wordpress.org/trunk@27287 1a063a9b-81f0-0310-95a4-ce76da25c4cd
maybe_regenerate_attachment_metadata() is now wp_maybe_generate_attachment_metadata().

props kovshenin.
fixes #26825.

Built from https://develop.svn.wordpress.org/trunk@27441


git-svn-id: http://core.svn.wordpress.org/trunk@27288 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fourteen: Add a .button class.

props celloexpressions.
fixes #27075.

Built from https://develop.svn.wordpress.org/trunk@27442


git-svn-id: http://core.svn.wordpress.org/trunk@27289 1a063a9b-81f0-0310-95a4-ce76da25c4cd