Sort city religion overview by number of followers

Made Prince difficulty "truly balanced"

Modding: 
- "Not shown on world screen" applies to promotions and statuses
- "Never appears as a Barbarian unit" also affects upgrades
- Remove great person point accumulation for units no longer available in this ruleset
- Allow atlas generation when using --data-dir option (e.g. Windows, installed via MSI)

Correct puppet city description - By Ouaz