webadmin: Refactor QoS view side

The business entity and model aspects of QoS were recently refactored
into a reasonable class hierarchy, this does the same for the view
aspect of things to ease implementation of additional QoS dialogs
(e.g. host network QoS).

Change-Id: Ia6c3be8a4ed4378ef10512fbef3e5a7e17f521a4
Signed-off-by: Lior Vernia <lvernia@redhat.com>