engine: support for adding network qos for rest-api

* NetworkQoS will override QosBase
* Move NetworkQos dao to use QosBaseDao
* Move network_qos data to qos table, and all its references
* Move network qos CRUD command to use qos infra

Change-Id: I34f43f9edc10b7b52e096b2b6f1f43d19f129ed5
Bug-Url: https://bugzilla.redhat.com/1078863
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>