Replace `wrap-type` and `wrap-length` by an unified entry.

[someth2say]

What's a little suboptimal in the design of the new setting is that you can now set wrap-type = none + wrap-length = 80 and the outcome will be that the content will not be wrapped. Or wrap-type = sentence + wrap-length = 80 and it will wrap at the end of sentences, even if they're longer than 80 characters. It would be neater if there was a single setting that did not leave such a potential for errors.

[fellen]

Hi, I come from PR #13. after before complaining at opensuse. My problem as a maintainer of https://github.com/Gnucash/gnucash-docs: we have still to support contributors, who have the kitebird version installed.
If I add to

*DEFAULT
  wrap-type = length

that version returns Unknown option name: wrap-type

Perhaps some mapping should be done:
wrap-length = 0 -> wrap-type = none
wrap-length > 0 -> wrap-type = length
and you could add:
wrap-length < 0 -> wrap-type = sentence

[someth2say]

Thanks for the request!

I feel you, and I start seeing many people requesting backward compatibility with the Kitebitrd version.
I'm going to re-open #13 and start thinking about different options we may have.

I feel adding extra semantics to wrap-length will be confusing, so I am inclined to consider @sknorr proposal of making length the default wrap-type.
I need to take a deeper look at it and make a decision.

As a side note, I would (indeed) recommend upgrading XMLFormat to this version.
I see your project distributes a copy of Kitebird's version, so just changing it to this one should be enough.
Anyway, I foresee some of your contributors have Kitebird's version installed in their systems, and maybe replacing may be problematic.