This v1 marries Jetpack's Site Icon module with the Media Modal, reusing code
from the Custom Header admin. For now, the core-provided icons will be limited
to a favicon, an iOS app icon, and a Windows tile icon, leaving `.ico` support
and additional icons to plugins to add.
Props obenland, tyxla, flixos90, jancbeck, markjaquith, scruffian.
See #16434.
Built from https://develop.svn.wordpress.org/trunk@32994
git-svn-id: http://core.svn.wordpress.org/trunk@32965 1a063a9b-81f0-0310-95a4-ce76da25c4cd
