US2807 - Add docs that explain how to configure Pulp to work with a given broker config.

The intent of this story is about configuring Pulp to work with a given broker config, and not about configuring the broker for a given config. Assuming the user has a specific Qpid or RabbitMQ installation in place, this guide can tell them how to do the Pulp portion.

I originally wrote the settings for the [task] section, so I can vouch for their correctness. I believe the [messaging] section is correct, but I had to read up on those settings, along with some notes I got from @jortel.

One known gap is that it doesn't talk much about the rpm installation for Qpid transport. I have a future PR planned that is going to fill that gap through the creation of a new groupinstall command. That is considered separate work.

I also fixed a few docs errors that were causing warnings and errors. With this PR docs built from scratch will experience no syntax errors or warnings.
comma before "which"