DRY-refactor notification display conditions

* Condense the different notification icons into one span with a
  dynamically selected ng-class.
* Move logic for determining which notification icon to show and whether
  there are no notifications into AuthCtrl.
* Refactor out the two similar sequences of logic conditions into a
  helper function.
Add unallocated attribute points notification

* Uses i18n "haveUnallocated" string, to come in another commit
Make attribute referencing in notification logic more robust
Merge pull request #4112 from betaveros/unallocated-notification

Notification for Unallocated Attribute Points (fixes #4109)