Add Storwize replication group support

[OpenStack Infra]

https://review.openstack.org/469394
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/cinder" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit 24e4c3ea684c7d418c2de5ac8c46d175819a4b42
Author: Xiaoqin Li <email address hidden>
Date: Wed May 31 17:22:02 2017 +0800

    Add Storwize replication group support

    This patch adds consistent replication group support for
    Storwize/SVC driver.

    Supported operations:
    * Create replication consistency group
    * Add volume to existing replication consistency group
    * Adjust existing replication consistency group
    * Enable replication on group
    * Disable replication on group
    * Fail over replication group back and forth

    DocImpact Implements: blueprint replication-cg-svc

    Change-Id: Id8d886feca938e99df14c35b17826b24d7c2b584

[Sean McGinnis (sean-mcginnis)]

Please add updates for the documentation or close if this was created in error.