made admin/includes/slide_form.php
modifed admin/slide.php to require_once admin/includes/slide_form_validate.php (empty at the moment)
fixed typos in slide_form.php: available -> availability
modified slide_form.php: changed price field maxlength from 5 to 4
made slide_form_validate.php: defined validation functions validName() and validPrice()
made a ton of changes. need to figure out image upload, image validation; need to update htaccess;