LPS-46787

@brianchandotcom

I want to send you this pull request first to review the new database schema for UserNotificationEvent. We want to split the original table into two tables. One is NotificationEvent, which will store the information of the notification, and the old table will remain as UserNotificationEvent. This will allow one NotificationEvent to be sent to multiple Users. 

However there is already a class in portal called NotificationEvent, so I know we have to change the name for one of them. I want to see if you have any insight on what we should do.

thanks