Baby steps: `Database` should have an `_init()` method...
Seems like this should be next to `value()`, based on convention...
Big step: the `_formatters()` method returns a hash of "formatter" closures that are injected into `$_columns` in `_init()`

This implementation of `_formatters()` just handles the date-like values: `datetime`, `timestamp`, `date`, and `time`.
Now there's no need for that oddball `_toNativeBoolean()` method, either.
The Postgres adapter is the only one that uses the now-deprecated `_toNativeBoolean()` method.