Create the QoS API extension stub

Create the QoS API extension stub

This patch introduces the QoS API extension, in a basic
form where we could, in combination with the service plugin
stub, start creating some experimental test jobs that install
the service plugin.

Please not that URL mapping is not fully according to spec,
neither it does include any testing. We need to work that out.

blueprint quantum-qos-api
Change-Id: I86e8048e2d9b84690dbede9a94cfc884985069c5