:sat and :prove print counterexamples in the user-configured number base
REPL handles printing of :sat/prove results; parenthesize predicates as appropriate
Update regression tests for :prove and :sat output

As of ee8685e4f283968b236b9328b43b5d72eb49cee6, :sat and :prove now
parse and then pretty print the given predicate with appropriate
parenthesization.