Cost enablement/disablement and some feedback quality of life changes.

• Fixed some page redirects for the edit stock page. Now diverts you to the stock main page if all is successful, else drops you back on the edit page.
• Cablestock description is now optional. This is not always relevant to the item.
• Stock.php now has response handling built in. This means that error messages will show correctly.
• LDAP settings on the admin page now has the correct error checkind and response handling. There are a couple of unique ones left in place.
• Can now disabld / enable the cost for items. This is not always needed so can be toggled off under stock managemet in admin.php.