Implement Notifications for Ember

closes #2417
- Adds NotificationsView
- Shows notifications in application.hbs
- Adds notification view

This PR implements notifications as per #2417. 

I'm trying to implement something similar to: http://stackoverflow.com/questions/14288980/global-notifications-view-using-ember (componentFor however is deprecated - but the idea should be clear).

Notifications are implemented as a ComponentView with a custom itemClassType to render individual notifications. 


![selfie-1](http://i.imgur.com/1VrJgK1.png)