Added Mark all in filter as read feature

Integrated feature
Added tests
In response to a users request(Issue #5113) i have added a feature that allows users to mark all notifications in the current notfication filter they're on as read without marking all the others read, i have also added tests for this feature in spec/controllers/notifications_controller_spec.rb
This specific code breaks the notifciations routes, but i did clean it up a bit to
```
  resources :notifications, :only => [:index, :update]
  get 'notifications/read_all' => 'notifications#read_all' 
  get 'notifications/read_all_shown' => 'notifications#read_all_shown'
```