[What's New] Simplify config object

[BillWagner]

The config object has grown slowly with each new feature and changed behavior in the tool. At this point, a number of config options could be flattened or removed. Some currently required options could be made optional.

This should be one update for config, because it may include breaking changes in repos where the tool is installed or used. While we should minimize breaks, they may be the right choice in this instance.

See #254 (comment)