Initial draft of federated plugin

TODO: add user provisioning module - Kristy
Merge branch 'federated_auth_plugin' of https://github.com/kwss/keystone into federated_auth_plugin
Merge branch 'federated_auth_plugin' of https://github.com/kwss/keystone into federated_auth_plugin
Added user management module
Merge branch 'federated_auth_plugin' of https://github.com/kwss/keystone into federated_auth_plugin
Added support for phase parameter in the federated auth plugin