Use local date format for display

[peter88213]

Currently (v3.0), novelibre uses YYYY-MM-DD, according to ISO 8601.

This is an example for getting the localized date format:

import locale
from datetime import datetime
locale.setlocale(locale.LC_TIME, "")
datetime.fromisoformat('2024-03-12').strftime('%x')

This format could be used for the tree view and the section list.
In the section properties, it could be displayed along with the weekday.