Todo-cli-tddschn

Changed
- Change to use `yaml` config. [Migration Guide](migration.mdmigrate-to-v200).

Added
- Support hiding specific columns in the `ls` and `get` commands.

Added
- Custom date formatting
- `--full-date-added` to display full date and time for the `ls` command
- You can also specify date format strings in the config file.
Changed
- Smarter default date formatting: Omits year if it's the current year.

Added
- A new `todo` property: `date_added`.

Requires manual migration with `alembic`, see [Migration Guide](migration.mdmigrate-to-v100) for more info.

- `utils` sub-command:
- `export` todos to `todo add` commands that can be used for re-construct your todo database.
- `fill-date-added-column` to fill `date_added` column of the `todo` table during migration

- `todo ls`: more filtering options, including `--due-date-before` and `--date-added-after`.