Use correct cache setting with swift authtoken

fixes bug 1131433

As noted in the bug report, bad things happen if
the wrong cache value is used with the authtoken
filter.

See associated update in swift repo:
https://review.openstack.org/#/c/22615

Change-Id: I979a9d7bce12867b3ec2dc303c4df74678ee9798
Add information about pluggable auth handlers

fixes bug 1084497

This patch adds a new file and includes it from the common
keystone chapter. Grizzly brings the ability to use the auth
handlers from apache-httpd, and this change takes docs from
the keystone repo to make them available for operators.

Change-Id: Ife00dfb48ec717598b545ee1ffc1ccccaa89b6ad
Merge "Add information about pluggable auth handlers"
Merge "Use correct cache setting with swift authtoken"