fix/add script to fix date formats

[aspedrosa]

Closes #231

Do we really need this?

As long as date formats are not corrected in CatalogueExport, this script will still be required to convert all dates to a common format, unless such process is done manually.

Usage

1. Enter inside the dashboard container

2. $ python manage.py shell

3. from utils.fix_dates import apply_changes
   apply_changes()

Note: github actions errors addressed on #243