Add non-null setting to BlackCard#body.
Add scaffold for CardSet model.

This will represent a set of C.A.H. cards (e.g. Base Set, Expansion).
Add scaffold for WhiteDeck model.

This will represent the deck of White Cards in a C.A.H. game.
Add scaffold for BlackDeck model.

This represents a deck of Black cards in a C.A.H. game.