Adding documentation for AWS Config service

It's a topic name that our code currently looks for.  And, it's something that Amazon says has to exist *before* they enable the AWS Config service (which is why it's a manual step now).  Amazon doesn't care what the name is, so we could request a more miq-y name.

As a side note, we do create an SQS Queue that pulls messages from this topic and that queue name is very miq specific.