Added an Agent focused on making good trades and playing all its mana every turn

This PR doesn't mean I think you should merge this in; it needs cleanup and more functionality even if you want to add it. It's more of an FYI. It's still braindead about placement, spells, non-Warlock hero powers, etc.

TradeAgent beats RandomAgent 90-95% of the time in a mirror match with the example deck.