Enforce unified values for Organization.classification

[girogiro]

API should refuse values not among the allowed ones for Organization.classification listed in Scraper development guidelines for Visegrad+ project. The list of allowed values is needed to add to Organization schema in schemas/organization.py.

However, existing incorrect values must be corrected in the database first and all scrapers checked and fixed to use only the allowed values which is not the case now. Also check that the terms parliamentary group and party are not misused by scrapers.