Smoother Difficulty 1.4

Largest update yet!
- Two new difficulty levels: Demi-god is between Immortal and Deity in AI strength, and Omniscient is harder than Deity
- AI no longer gets any extra settlers on Deity or Omniscient
- On Emperor and higher, AI now gets extra amenities in all cities over the course of the game
- On Immortal and higher, AI combat bonus now increases over the course of the game
- On Deity and higher, the player gets a production penalty (special thanks to MyopicCat and his mod Diety++ for the amazing idea)
- All bonuses that depend on game era (science, culture, and now amenities and combat strength) now depend on each individual AIs progress, instead of the progress of the game leader. An AI in the Medieval era will only get era-scaling bonuses from Medieval even if someone else is in a later era.

Small update to fix tooltip errors for combat bonus of Immortal and Deity difficulties, as well as make the mod code structure a little more intuitive. This shouldn't change any actual in-game combat strength. Note that this will affect new games only (old saves will still work the same and still have wrong tooltips)

- Production and gold scaling reverted from 0,0,0,30,60,90,120,150 to 0,0,0,20,40,60,80,100 because it turns out bonuses are capped at +100% and don't do anything beyond that.
- To compensate for this loss of production and gold, AI combat bonus increased at Immortal (+3 -> +4) and Deity (+4 -> +6)
- AI science and culture now scales based on era.

Era | Warlord & Lower | Prince | King | Emporer | Immortal | Deity
Ancient | +0% | +12% | +24% | +36% | +48% | +60%
Classical | +0% | +13% | +26% | +39% | +52% | +65%
Medieval | +0% | +14% | +28% | +42% | +56% | +70%
Renaissance | +0% | +15% | +30% | +45% | +60% | +75%
Industrial | +0% | +16% | +32% | +48% | +64% | +80%
Modern | +0% | +17% | +34% | +51% | +68% | +85%
Atomic | +0% | +18% | +36% | +54% | +72% | +90%
Information | +0% | +19% | +38% | +57% | +76% | +95%

Thanks to Atlas627 for the idea.

To counteract the reduced number of warriors, AI now get a small combat bonus vs barbarians. +1 vs barbs for each difficulty level past Prince.