LPS-45890

Please reconsider this pull request. 

We need to use deliveryType (see UserNotificationDelivery in service.xml) to tell the different type of deliveries (see UserNotificationDeliveryConstants.java). The existing type is used for portletId or classname to indicate whether if the notification is blogs, MB, wiki, documents. The field type was legacy, and I would rather keep it the same. I feel like adding a new field is not that bad especially this is for 7.0

For 6.2 we can use a hook like we did in so-activities-hook and achieve the same thing. For 7.0, we should keep it in portal since this is needed for the framework. Later on we can move this to a osgi mdoule.

Thanks