Remove old admin webui and related files

webui/group-add.php

webui/group-attribute-add.php

webui/group-attribute-change.php

webui/group-attribute-delete.php

webui/group-attributes.php

webui/group-delete.php

webui/group-main.php

webui/group-users.php

webui/images/bg.jpg

webui/images/bullet.jpg

webui/images/help.gif

webui/images/menuleft.gif

webui/images/menuright.gif

webui/images/specs_bottom.jpg

webui/images/strips_onside.jpg

webui/images/top2.jpg

webui/images/valid-css2.png

webui/images/valid-xhtml10.png

webui/images/wcag1AAA.png

webui/includes/config.php