Future of Raft configuration doc

When the orderer section of the deployment guide is merged, one of the purposes of this doc: https://hyperledger-fabric.readthedocs.io/en/release-2.2/raft_configuration.html

Will be superseded by it.

This Raft configuration doc does a few things other than talk about initial orderer parameters (which is the limit of the scope of the deployment guide), however. It also talks about:

- Channel configuration parameters relevant to the ordering service.
- Adding a new node to an ordering service.
- Certificate rotation.
- Hidden parameters.

I would suggest that, long term, the process for adding a node to an ordering service should be its own tutorial, and that likewise rotating certificates is worth of a broader operations guide topic talking about more than just ordering nodes.

The hidden parameters and channel config parameters would seem to belong in a reference topic.