Adding Support for determining when the game is Over

1. Before making any mobe a check is made to see if King is in Check
condition
If so, King is moved
2. After a piece is moved if the opponent's piece is killed,
noOfDeadPieces and noOfAllivePieces is updated.
3. GetInstance was not populated correctly, this is fixed.
4. Support for Pawn's diagonal move for killing opponent's piece is added.
5. The game stops if either of the Player's king is killed

Signed-off-by: Mayuresh Janorkar <janorkar@usc.edu>