Using the standard (type class based) transitivity tactic for more contr...

...olable proof terms. As discussed in #454.
cbn -[foo] would work, but [cbn term/@cst (at x)?] is not currently handled, as it requires finding an applicative context with term at it's head and counting occurrences. We're thinking of making cbn an (optional, but by default) alias for simpl once this is resolved.