Add domain authorization scope

[bblrlo]

Add domain authorization scope as discribed in http://developer.openstack.org/api-ref-identity-v3.html#authenticatePasswordScoped

[bblrlo]

json request must be like this: { "auth": { "identity": { "methods": [ "password" ], "password": { "user": { "domain": { "name": "domain-name" }, "name": "usr", "password": "pwd" } } }, "scope": { "project": { "domain": { "name": "domain-name" }, "name": "prj-name" } } } }

[carolynvs]

Looks like this is specific to identity v3, which is on our roadmap but isn't implemented yet. When that is tackled, I'll make sure this is included.