Organization of Output to the Console

[mlesnick]

Currently, the bigraded Betti numbers and Hilbert function are both printed together when rivet_console is run with the option --betti.

IMO this is not great design: It should be possible to print the Hilbert function on its own, and it seems weird to name the argument "--betti" if the Hilbert function is being printed as well.

Also, it should be possible to print the Betti numbers, Hilbert function, and minimal presentation in a single computation.