BUG: Return local Timestamp.weekday_name attribute (#17354)
- [x] closes #17354
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

@jreback created a new method `_get_named_field` based on your [comment](https://github.com/pandas-dev/pandas/issues/17354#issuecomment-325319229) in the issue thread.