Add topic in Operations Guide on using the orderer management APIs

Current documentation has 2 versions of the create a channel tutorial

- Create a channel
- Create a channel with the test network

The first version describes both how to configure your orderer so that you can use the orderer management APIs or remove the system channel from an existing orderer. Then it describes how to use the osnadmin channel commands to create and manage the channels.

The second version describes only how to use the osnadmin channel commands to create a channel based on the test network which has a single node ordering service without a system channel.

We could consider combining the 2 tutorials or only having the second tutorial, and adding the information from the first tutorial into an ops guide topic instead. That is what this work item is for. Topics to include would be

- describe in detail how to configure an ordering node
- considerations around joining additional ordering nodes to the channel
- removing the system channel from existing ordering nodes