Revert _admin_bar_preferences() and add a class to the table row to allow it...

Revert _admin_bar_preferences() and add a class to the table row to allow it to be hidden. Forcing the use of CSS at least attempts to ensure that the developer will recognize that the saving aspect isn't handled. Handle this in the future across all settings screens. Reverts [17161]. fixes #16004.

git-svn-id: https://core.svn.wordpress.org/trunk@17234 1a063a9b-81f0-0310-95a4-ce76da25c4cd