Option to include "ch"-Prefix in latex

[david-jointech]

The changes-latex-package offers the option to add the "ch"-Prefix to commands. Thus \added becomes \chadded and so forth. This is supposed to fix conflicts with other packages, in particular regarding \comment and \highlight.

It would be nice to have such a flag in pancritic too.

Right now I'm using a lua-filter for my further pandoc-generation, which transforms occurences of \added to \chadded (and so on). But this is error-prone and probably also takes away some extra performance unnecessarily.