HOTFEATURE: Custum Field Fixes And Options

Several adjustments to custom field behavior and a new option has been added.

FEATURE:
Custom fields can now be made readonly. There are multiple levels: Off, Admin, API, or Not Writable.

* Off is the default behavior. The field is fully writable by the frontend, admin, and API.

* Admin Writable means that the field can only be changed by users in the admin console and via the API.

* API Writable means that the field can only be changed by the web service API (this still needs some testing and will be adjusted in the next few days)

* Not Writable means that no one within the app or API can change the field. It is accessible only via direct db access (in other words, we'd be the only ones who could change these, this still needs some testing and will be adjusted in the next few days).

Custom fields appearing as readonly do not trigger validation and are skipped while saving. These fields are grayed out when displayed.

FIXES:
Added more “tip text” on the Custom Field editor page to better understand each field.

Custom field labels (display names) will now appear in the tip text of the custom field on editor pages.

Custom fields triggering field validation now display error field highlighting like normal fields.

Custom fields are no longer validated at the Biz layer of the app. They are now validated in the user interface. They can still be validated via the CustomField.ValidateInput() method by custom code, if necessary. This was done to remedy situations where a customer will set a field as required and cause imports, Google Checkout orders, and other places where custom fields may not need to be validated to fail.

Fixed an issue where the error area of the EditDetails page on the frontend (the custom field editor from MyAccount) would display even when there were no messages.