Reintroduced changes from changeset [520] and [540] wich where overwritten by changeset [546]
Revoked changeset [541] end removed all PAGE_EXTENSION variables and the related option in WB settings as this function only works on Apache Servers together with .htaccess and mod_rewrite...
fixed two issues with menu_link: adding a menu_link as first page did not worked; and an E_NOTICE-warning
module menu_link: fixed page-deleteing-bug and some odd behavior, added table mod_menu_link