Fix AI Luxury Improvement issue with Monopolies and Corporations Game Mode
This mod fixes the luxury improvement issue the AI has with the Monopolies and Corporations Game Mode by moving corporations to currency. I noticed that the AI worked correctly when you reached economics, so tested moving the requirements for corporation to pottery and AI went on improving everything normally. I decided to move it to Currency as it wont have a lot of effect on the game, as you need a great merchant to create a corporation anyway, and it turns out even if you have one it does restrict the creating until you actually reach economics. So fix works great.
