Ready: State vs. operations in the Data Types doc

In a Twitter conversation, it became clear that we don't make it clear enough that DTs are operations based *only from the standpoint of clients*. Behind the scenes, they are state based, as they should be. I'll make this more clear and do some other clean up as well.
I'd like to disambiguate "actor" and "pairwise maximum" in the Counters row above. Suggested rewrite:

> Each actor keeps an independent count for increments and decrements; upon merge, the pairwise maximum of each actor will win (e.g. if one count for an actor holds 172 and the other holds 173, 173 will win upon merge).

The key is, you're not comparing actors, you're comparing the count for each actor (which is what pairwise means in this context).