AI system does not work well

[nhoxbypass]

AI system for letting computer to play VS player currently does not work very well. There are something need to improve:

• When select computer mode in Game setup dialog, the program logs out that AI is "thinking" but player can still play and move the opponent chess.

• MiniMax algorithms is not implement efficiently, time to calculate next move is too long even when this is the first move. We need to improve it or use some other algorithms like AlphaBeta,...

• AI system is not like a "system", this is too separate functions, we need to refactoring the code.

[nhoxbypass]

Currently the issue that player can move opponent's chess even in AI mode is fixed in commit https://github.com/USAssignmentWarehouse/Chess/commit/6d5377c1b2ad87f68139764309c89d7da7aaa7dc.

[nhoxbypass]

This issue is closed in Pull request https://github.com/USAssignmentWarehouse/Chess/pull/4