New plugin manager half-implemented. Most of the UI/frontend code is done. Moved sql_parse.php to /includes/ to allow use after installation - TODO: check installer, etc. for breakage

<?php

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