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
Looking at this again we can slightly clean this up by exploiting that we can call `where` multiple times:

```ruby
notifications = Notification.where(recipient_id: current_user.id)
notifications = notifications.where(type: params[:type]) if params[:type]
notifications.update_all(unread: false)
```