Add pipeline configuration for tempurl with swauth

The pipeline needs tempurl added before the auth middleware (swauth).
In addition we need to set allow_overrides=true when using swauth and
tempurl. This change introduces an attribute which an be overridden to
make both these changes.

* Add toggleable attribute to configure tempurl + swauth
* Update README with attribute info
* Add condition to proxy-server.conf template to insert tempurl into
     pipeline
* Take account of new dynamic role attribute
        [:swift][:management_server_chef_role]
* Correct name spelling

Change-Id: I035793230372c1a02de5f906f2ff6dde9f27d3ab