Clean or scramble user extra profile fields

[tmuras]

Data in extra user profile fields is not cleaned. I would suggest to do something simple - e.g. just delete all the extra data with equivalent of: TRUNCATE mdl_user_info_data;

This should be an extension to moodle-local_datacleaner/cleaner/users/classes/clean.php I believe; Let me know what do you think and I can work on a patch.