Nathan

Results 7 issues of Nathan

## Summary The current docstring for `to_string()` does not provide detail on how missing values are handled when using `formatters`. This change adds an additional block to the `formatters` docstring...

Docs
Styler
Stale

Some misc cleanup work from August last year

- Updated accessors and added compatibility wrappers - Renamed variables in GPS week derivation function for clarity - Updated and extended unit tests