In order to proceed with switching flavor in OSC from novaclient/self
api onto SDK few new methods need to be supported.
Those include flavor access and set of extra_specs related operations.
While extra_specs in terms of SDK should be a separate resource, it is
not easy to implement it this way. On the other hand all those
operations are definive subset of flavor related operations.
In addition also merge FlavorDetail into Flavor class
Change-Id: Ia4f60acce5e0e5665e2ba704fe4cd0ec81437eb5
5805b461eb