Currently the identity administrator guide docs are a part of
general OpenStack-manuals. Migrating those docs to keystone
documentation so that they can be reviewed effectively by
keystone developers too.
Partial-Bug #1694460
Depends-On: Ia750cb049c0f53a234ea70ce1f2bbbb7a2aa9454
Change-Id: Id121ae1dd5bce993b4ad1219b592527ef0047063