Handles adding new spiders and editing details for existing spiders

• Accessed at ?action=admin;area=sengines;sa=editspiders or ?action=admin;area=sengines;sa=editspiders;sid=x
• Also called from ViewSpiders when $_POST['addSpider'] is set
• Uses the spider_edit sub-template
• Redirects to ?action=admin;area=sengines;sa=spiders
• Re-sorts the spiders table and re-caches the data