Updates to the architecture doc
Updates to the architecture doc

The text in the architecture doc is somewhat out-of-date for the
current function level of keystone. Edits include:

* Removed references to domain, project, role information in LDAP.
* Removed capitialization of keystone objects
* Some line wrap adjustments
* Updated link on oslo.policy location

Change-Id: Iefcaf00c8844613b10a2cf77a820db7fe0934742

rajalokan/keystone,mahak/keystone,ilay09/keystone,ilay09/keystone,openstack/keystone,mahak/keystone,openstack/keystone,ilay09/keystone,rajalokan/keystone,openstack/keystone,mahak/keystone,rajalokan/keystone