Adding column_date_formats config option

[dougharris]

Description

Allows per-column formatting for date, time, datetime like columns.

Add a column_date_formats section to your config file with separate lines for each column that you'd like to specify a format using name=format. Use standard Python strftime formatting strings.

More details in #1402

Checklist

• I've added this contribution to the changelog.rst.
• I've added my name to the AUTHORS file (or it's already there).

• I installed pre-commit hooks (pip install pre-commit && pre-commit install), and ran black on my code.
• Please squash merge this pull request (uncheck if you'd like us to merge as multiple commits)