[Core] Adds notification management.

* Adds Controller Plugin (enhancement of FlashMessenger)
* Adds View Script to render notifications (through Model injected by a listener to
  the render event.)
* Adds View Helper to render Alert boxes.
* Refactors HeadscriptInitializer to HeadscriptFactory
  (allows for route-aware script injection via config file)

(refs gh-28, #5101)
[Auth,Applications,Jobs] Uses new notification management system

(refs gh-28, #5101)
Merge branch 'feature/General-notification_management' into develop