Make sure all container topics contain sufficient content

[dedemorton]

Some container topics contain a short description to introduce a group of loosely related topics.

If the topics are loosely related, add a list of links in the container topic that point to the topics covered in the section. We don't currently automate the generation of this list, though, so it will need to be updated whenever topics are added or removed.

If the topics are closely related and users are likely to want to access all of the topics together, then use float tags to combine the topics into a single file.

[dedemorton]

Closing in favor of tracking this issue in #2482