Added option for subclasses to provide default_model() that will be prepended to the user model (merged).
Added option for subclasses to provide default_model() that will be prepended to the user model (merged).

zejn/cubes,cesarmarinhorj/cubes,pombredanne/cubes,zejn/cubes,she11c0de/cubes,pombredanne/cubes,ubreddy/cubes,noyeitan/cubes,jell0720/cubes,she11c0de/cubes,ubreddy/cubes,noyeitan/cubes,jell0720/cubes,pombredanne/cubes,cesarmarinhorj/cubes,cesarmarinhorj/cubes,jell0720/cubes,she11c0de/cubes,noyeitan/cubes,ubreddy/cubes,zejn/cubes