Cultures: Supergroups

[LordPeter]

(Not to be confused with Metagroups, which are a scripted backend system for use in events.) "Supergroups" would be larger groups that encompass several culture_groups, and provide an opinion bonus between those, effectively simulating a third layer above those currently ingame. This would help to mitigate gameplay upsets from the culture group splitting. An example would be e.g. "Slavic" which consists of west_slavic, east_slavic and south_slavic, and provides <culture_group>_opinion boni between each.

• [ ] decide on what culture_groups should make up a "supergroup"
• [ ] implement opinion boni between these
• [ ] provide opinion boni between "hybrid" cultures that should be part of 2 culture_groups. Examples would be Nepali (in Central Aryan, bonus towards Tibetan group), Occitan (Occitano-Romance, bonus towards Gallo-Roman) and Catalan (Occitano-Romance, bonus towards Iberian).

[LordPeter]

This issue is dependent on the cultural setup being finalized. Thus before work can start here, issues #20 #21 #22 #23 & #25 need to be resolved first.