Added tab-based interface to userpage UI. Yes, it is plugin expansible, and yes, it breaks existing plugins that add code to the userpage (but that can be fixed with a "colspan=4")

<?php

class Text_Wiki_Render_Plain extends Text_Wiki_Render {
    
    function pre()
    {
        return;
    }
    
    function post()
    {
        return;
    }
    
}
?>