Add flavor create and delete API calls for openstack-nova

1. Update FlavorApi and FlavorAsyncApi by adding create(...) and
delete(...) methods
2. Add CreateFlavorOptions class
3. Add flavor_new.json and ParseCreateFlavorTest
4. Add create and delete tests into FlavorApiExpectTest

Change-Id: Ibf5fac95635cfc29d37831f31673909c2577edc7