Add PlayGame method in Game class.

Add PlayerType to distinguish Bots and real players.
Bot class to distinguish more intelligently bots and players.

Refactor Game class in consequence.
Remove useless code

Throw exception in case of a strange non reproductible bug...
Merge branch 'UI'
Revert "Merge branch 'UI'"

This reverts commit 36e7735e753a48d9ed207ed8935abf65092c3023, reversing
changes made to 0c57a90a71ea2556a07e1995ff794bc1fbe7cfc9.