About page design, first pass.

props melchoyce, ryelle.
see #27713.


git-svn-id: https://develop.svn.wordpress.org/trunk@28127 602fd350-edb4-49c9-b593-d223f7449a82
Inline documentation for hooks in wp-includes/media.php.

Props scottlee for the initial patch. Props kpdesign, DrewAPicture.
Fixes #27718.


git-svn-id: https://develop.svn.wordpress.org/trunk@28128 602fd350-edb4-49c9-b593-d223f7449a82