Moved board images to images directory

Moved j0.. j9.png to the images folder.

Changed the following line(s) in Board.java:
img[i] =(new ImageIcon(this.getClass().getResource("j" + (i) +
".png"))).getImage();
to:
img[i] =(new ImageIcon(this.getClass().getResource("images/j" + i +
".png"))).getImage();