A PlayerImpl is now required to have a MoveStrategy.
Added documentation to constructor in PlayerImpl.
Added toString().
playerIdToPrintableTag can now be accessed through a public method.
OthelloImpl now has a pretty toString().
Added singleton instance of OthelloCreatorImpl.
Updated uses of OthelloCreatorImpl in OthelloLab2IT to only use
singleton.
Added toString() in NodeImpl.
Updated toString().
Added equals() and hashCode().