Add method for fetching unread notifications

* This will be used for the unread notifications in message overlay

* This will be used to "mark all as read" based on sections ( event types ),
  since we can't do updateJoin.  We could set a max update limit like 3000,
  and use this to do "mark all as read", this would handle majority "mark all as read"
  use cases. This would also prevent updating big amount of data on a web request

Change-Id: I2a9103a73d0aa91a52d5c0233e946a0ef979f96d
Merge "Add method for fetching unread notifications"