Add cookie-based authentication along with X-Auth-Token

- added jquery.cookie as Bower dependency
- fixed keystone.py middleware to process the cookie and inject X-Auth-Token
  into the request, X-Auth-Token still has priority though
- fixed 401 response format to return iterable (list)
- added test_auth_token for testing both authentication methods

(cherry picked from commit 9a8d01ff1ac54bb9c3c737bdb9ff5c0a688f3013)

Conflicts:
	nailgun/bower.json
	nailgun/static/js/main.js

Change-Id: I01239c93b8f0d5da95424d44c96f6fb60ab378fd
Implements: blueprint access-control-master-node-improvments