Fix some Insert-into-Post for Audio/Video bugs.

props wonderboymusic. see #23831.

git-svn-id: http://core.svn.wordpress.org/trunk@23870 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add "Customize" as first item under Appearance menu.

fixes #21413. props ryanhellyer, obenland, DrewAPicture

git-svn-id: http://core.svn.wordpress.org/trunk@23871 1a063a9b-81f0-0310-95a4-ce76da25c4cd