Introduce [audio] and [video] shortcodes, and use MediaElement.js to play them.

props wonderboymusic. see #23282.

git-svn-id: http://core.svn.wordpress.org/trunk@23729 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Pass post format as a class to TinyMCE's body, props adamsilverstein, fixes #23198

git-svn-id: http://core.svn.wordpress.org/trunk@23730 1a063a9b-81f0-0310-95a4-ce76da25c4cd