QoS API and DB models

* Contains a skeleton for the REST API - Sean still needs
to learn about how to use the RESOURCE_ATTRIBUTE_MAP.

* Implements a vendor neutral database model centered around a QoS
object, that has a policy field that can store arbitrary JSON.

* QoS objects can be linked to Networks, Subnets, or Ports.

* QoS mappings to a port overrides a subnet policy, subnet
policy overrides a network policy. If no policy is specified,
the policy is inherited from the parent object.

* Needs unit tests

Blueprint quantum-qos-api-db

Change-Id: Ia4d5c6cae82c579928129d0728cb03091d2869a7
Rename the Cisco QoS db table

Just moving it over here for a bit until I rework their
models to play nicely with the QoS db table and policy column

Change-Id: I68d18b7a066f622fbfbf273a6c692a1fd295f6c8