Enhanced Culture 2.0

Adds three new mechanics:

• Culture is accumulated on a civ-wide basis and used to trigger Golden Ages
• Some Buildings can now add an exponential modifier to Great People Birth Rate based on a City's Culture Level
• Some Buildings can now add an exponential modifier to Trade Route Yield based on a City's Culture Level

See thread for more details and discussion:

https://forums.civfanatics.com/threads/enhanced-culture.566926/