Deprecate `addState()` in favor of `withAttributes()`

[mpdude]

What is the semantic difference between using Factory::addState() and Factory::withAttributes()?

The former seems to simply dispatch to the latter.

Is there more intention behind it and should I be careful when I use which?

[kbond]

No difference, it's really just a way to be more explicit when writing state methods. I think I'd be ok to deprecate addState - wdyt @nikophil?

[nikophil]

yes, I'm fine with it, moreover, in the version with "split factories", addState() and withAttributes() are in the same class

[kbond]

Fixed in #493.