Add support for settings, aliases

This allows for passing settings to a brief when instantiating it, which
is how you can add aliases for keys on your brief.

Add `find` method

The `find` method accepts an array of keys, and iterates over the
returning the value of the first key that matches. This allows for some
itneresting behavior, such as defacto aliases for values or setting
built-in defaults.

feat(construction): allow passing of null/bool values