Setup Improved: Mementos for AI players

Edits the game setup menu so the AI start with mementos, and players can alter their mementos. A necessary part also was to resolve the randomness of AI civs, setting their leader and civ values. These are now viewable and editable on the advanced setup screen. Leaders/civs now have possible mementos to choose from, and its setup so modders can make auxiliary mods that alter or add additional combos. This does not affect multiplayer games. I haven't got the ability to test the multiplayer select screens but if it errored, I'd like to know. Note: A current issue with the memento editor means the popup starts unselected. But you can just click the slot while in the memento editor.