Media Grid, in the Edit Attachment modal: 

* Label the fields under the attachment a la the Edit Media page
* Move the audio and video previews above the info
* Remove the audio / video icon display. Unnecessary.
* Ensure that `width` and `max-width` are set for `.mejs-container`

See #24716.

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git-svn-id: http://core.svn.wordpress.org/trunk@28874 1a063a9b-81f0-0310-95a4-ce76da25c4cd