Port quota classes extension to v3 API Part 2

Ports the quota classes extensions and the corresponding
unittests to the v3 framework.

Adds quota class id to data returned by update which makes
it consistent with the behaviour of show.

Partially implements blueprint nova-v3-api

Change-Id: I7ca95e332933872ff20d719bf07dd10364510cbe
Merge "Port quota classes extension to v3 API Part 2"