Adding tests for black bishop common moves.
Updated JavaDoc for some classes.

 - Boards are no longer required to be in official initial configuration upon
   initialization.
 - Required getLegalMoves to include squares in which a capture is possible.
Adding test for white's capture scenario.

Found a mistake white previous getLegalMoves test --- we were adding the expected
Points to the Set returned by the piece! Corrected now.
Adding capture scenario test for black Bishop.