v2.0.0

Added more control over how city level affects influence. This is done by assigning workers.

• Priests increase influence directly.
• Tributes increase influence in another city but cost a lot of food.
• Merchants have two effects:
• increase food production in both sender and receiver cities
• move 1 influence from each city to the other
• Builders make colonies (and nothing else contributes)

These come with changes to the UI and the AI.