Description of problem:

In many cases, some groups of topics work well together to form a cohesive narrative. For example, a chapter on "SSL setup" can be composed of several topics:

* overview of SSL
* creating the SSL database
* choosing a certificate type
  * using a self-signed certificate
  * using a certificate signed by a CA

This chapter can be shared between multiple Content Specs, but only by adding the individual topics that make up the chapter. Most Config Refs and Admin Guides that require encryption instructions will likely need such a chapter.

However, as the number of Content Specs that use this group of chapters grow, editing the structure of the chapter (e.g. adding a topic, deleting  a topic) becomes more difficult. If changing the narrative of "SSL setup" requires the addition of a topic, say "using an unsigned certificate", that topic has to be added to ALL the other Content Specs where the "SSL setup" narrative is used.

To address this dilemma, other CMSs use "Topic Groups". This allows you to specify multiple topics as a unit, which can then be plugged into multiple TOCs or Content Specs. As a result, any fundamental changes to the structure of the group can be single-sourced.

I'd imagine that such a group can be created as a mini-Content Spec in PressGang, and then specified into a Content Spec later on?