Add a 'mark as unread' to all unread notifications and allow them
to be marked unread. These notifications will no longer be automatically
marked as read when the pages they refer to are visited.
Bug: T73564
Change-Id: I677d3c0399e46fd7c35531df1cc0e61db2d4eb1b
Split and refactor Echo network handling and create a proper API
layer for the UI to use consistently. Split Echo's API methods into
its own module so they can be loaded along with the initialization
script and manage the API requests.
Change-Id: I0526a14bb8cc0d9729a303e24ab6e43259cc86bb