Create a proper Game constructor.
Create a proper Game constructor.

Sensible & consistent defaults, support for an empty,
uninitialized game.
Edit zones so they are never overwritten, but Zone.set_content()
is used instead, which also preserves the zone name.

mhmurray/cloaca,mhmurray/cloaca,mhmurray/cloaca,mhmurray/cloaca