Add notifications page

[tplooker]

Is your feature request related to a problem? Please describe.

In order for a user of OSMA to have a view of any pending actions requiring the users input. A notification page should be added as a base page, here a list of any pending actions (e.g credential offers, new basic message recieved, proof request) will be displayed.

Describe the solution you'd like

Add a new page called NotificationPage which is a tabbed page to MainPage, this page should render a list of TransactionItems (support already in the app) for any pending actions/unread notifications in the app.