fixed a bug (and added test) for when a player has two of the same card, but the HandTracker only knows of 1.  If there's only one other additional player with Unknown, calculateCard
assumed that the player with 1 and the Unknown player each had one.  That isn't always the case as 1 (currently) stands for at *least* one.  For now, just commented out the function
and tests that check for this case with a future plan to create an additional case of "at least one".
since AppEngine is single threaded, support for multiple threads isn't helpful
modified the Trick to be inside the HandTracker struct for the AI
starting an iterative version of findcardtoplay
moved the "next" playerid tracking into the Trick struct