Consider rule names, make configurable

[rzach]

Not all rule labels are produced by macros, and the style file has two sets for them. Make that uniform.

Also as suggested in #11 by @catrincm, avoid Latin. ECQ is Explosion, TND law of excluded middle.

[rzach]

@catrincm that is an excellent point. What do you call Modus ponens? Modus tollens? Anything else that needs changing?

[catrincm]

Modus Ponens is such a familar term that it's useful for them to know that. Modus tollens too is relatively used (more than TND) and I don't know of any nice alternatives. It was just the TND and ECQ I was thinking about.

I've opened new comment about one further point on the choice of rules: #17.