Comment 8 for bug 1098685

For related bug 166953, I've added a blank <option> tag to the SMS carriers dropdown on OPAC holds UI, so that it defaults to that, if none is already saved for that patron.

To address this bug, I've refactored some plain vanilla JS form validation that keeps compatibility with existing code and checks to make sure that if any method of hold alert/notification is checked, that the user cannot proceed unless they enter the needed Phone/SMS number (or "address" as it's been referred to in the report title). It gives user feedback using a yellow background color highlight on the culprit/missing field.

Code is in user/cesardv/hold_notification_bugs