Added poker cards and decks

Currently, cards hold an integer and a null image.  I couldn't get the image files to work.  Test images (courtesy of Zak) are in the .decks.images package if you want to try getting it to work.

Decks consist of a name (String) and a Set of Cards.  The usage of Sets means we do not have support for duplicate values in a deck.

Right now we still have to tie the decks to the selector in the GUI, but that shouldn't be to hard.  The default constructor, Deck(), creates the default deck specified in the requirement, with values of {1, 2, 3, 5, 8, 13}.