adding support for new middlewares

See https://bugzilla.novell.com/show_bug.cgi?id=860030

1. There's no UI for them here, I'm not sure if it should be. (Raw config should be possible)

2. The default value for yield_frequency is set to 10 (master value), not 60 (havana value), based on latest commit to master:
https://github.com/openstack/swift/commit/892c226ce57a8367db46409fe35257ae41c558f7