Update reference to middlewarearchitecture doc

auth_token was referring to the middlewarearchitecture doc in
keystone developer docs rather than python-keystoneclient.

Change-Id: I7bfb3595097cc4a2a1061efe5c4480e06a499edb
Fix references to auth_token in middlewarearchitecture doc

The middlewarearchitecture doc was still referring to
keystone.middleware.auth_token, but the middleware was moved to
keystoneclient.

Also, corrected some other minor typos.

Change-Id: I270ea2ccc739596e99a4a852bff3b5b7d1c85c82
Merge "Fix references to auth_token in middlewarearchitecture doc"
Merge "Update reference to middlewarearchitecture doc"