Adding new div id=content per #114355, also changing if($something) to if (!empty($something)) per #112453

Major changes! Zen now allows subthemes to define their own node.tpl.php, node-type.tpl.php, block-type.tpl.php, page-loc.tpl.php, etc... Also rearranging the way that secondary style sheets are included as per #113184.

several changes including new background image for unpublished items, microformat for node creation dates, new classes for comment-by-author, comment-by-anon, node-mine, comment-mine. other minor changes