Optional description field for Groups in navigation

[bryanmccarty]

The ability to use groups to organize our sidebar into sections is great. However, we need the ability to add a short description to the Group. Ideally a short (optional) 4-5 word description that sits in small text beneath the "group" field.

Reason:
Our APIs are complex. As well as we've organized them into sections and pushed the headings to be clear, concise, and meaningful, we want our users to immediate understand the section without having to click in or expand. A short description would give us that ability and help get our users to what they're looking for quicker (while immediately understanding some core concepts).