Represents a playing card
from a set of cards {0..51} which map to cards having a suit
{0..3} <==> {SPADES,HEARTS,DIAMONDS,CLUBS}
and a face value {0..12} <==> {2..ACE}
Handles the storage and retrieval of program preferences
Note. '=' is a reserved character and may not be used
to name preferences or within their values.