Refactored the repaint() command in ChessPanel to avoid unneccesary repetition.
Added @Override flag to toString function in Location.
Added in allUnblockedMoves() as a public function in ChessPiece, to avoid unneccesary checking when looking for all moves.
Implemented allUnblockedMoves() for pawns.
Modified movesForPiece() to use the new allUnblockedMoves() function.