Add prefix for henforcer #558
Description
Per Zurihac I am now on a mission to get more tools contributing to our error index. First up is henforcer, which I'd like to request a prefix of HEN. I will open a PR for this soon-ish as I figure out all the right places to touch. By PR I mean to this repository. All of the changes are already in the henforcer repository at https://github.com/flipstone/henforcer