Authenticate via oauth

Add support to authenticate with keystone via oauth access tokens.

Change-Id: Ie0eb3290d71661852cc7774bcdb1eb56971987be
implements: bp add-oauth-support
Fix attributes ordering at v3/client.py

Fix attributes alphabetical ordering at
v3/client.py.

Change-Id: I1ca71a56a6a710b231a8ed770835d45d3cf01cda
Merge "Authenticate via oauth"