Rise of Mankind: A New Dawn Code

Improve AI city founding site valuation, bring it into line with increased coastal value tiles
Tweak city AI to be a bit more oppertunistic with very early game settlers & workers
Tweak city AI threat levels for barbarians (was considering barbarian threat to be the same as full war with another player, overestimating threat)
Fixed bug where diplomacy screen showed AI to have more gold than they actually had (thanks buck_beach)