Improve Super Extras UI

Problem/Motivation

When navigating to /admin/config/search/simplesitemap/super-extras, the UI displays irrelevant information.

Steps to reproduce

* Authenticate as admin
* Go to /admin/config/search/simplesitemap/super-extras
* Observe field set "This is a title" and its contents of "Add this is a description."

Proposed resolution

TBD

Remaining tasks

TBD

User interface changes

TBD

API changes

TBD

Data model changes

TBD