Math producers

[Rob Beezer]

No, I don't mean you folks writing research articles. I mean you folks who have
tools/features writing PreTeXt math.

Recent work (and posts) have described deprecations of #me, #men, #mdn.

Here's an example: WeBWorK problems have single line equations and they are not
numbered. So #me has been an approriate thing to come back from a WW server
when we convert a WW problem to a static version for PDF, EPUB, etc.

That'll still work, since we have the pre-processor intercepting these and
"fixing" them. But it might be better long term to have the PreTeXt coming back
from a WW server produced correctly as:

<md number="no"> some latex here </md>

I think there is a lot more.

* MyOpenMath

* STACK

* FITB (I edited some code inside a "toTeX()" function already.)

* More that is escaping me right now.

* More that I haven't even thought of yet.

It'd be great if we can get producers all producing "valid" PreTeXt. (And I
apologize that it is still a moving target.)

Happy to help with questions, but I think much of this is outside of PreTeXt
proper so there is not much for me to do.

Rob