Provide proper setup for Zipperposition, with the usual production quality standards.
Isabelle/aca85e8d873d already provides isabelle build_zipperposition from the OPAM entry version 1.6, but this is rather old.
Proper inclusion in Isabelle might require:
- to update the OPAM version
- or to change the isabelle build_zipperposition tool to build from the repository (this might be more work, due to OCaml dependency hell on multiple platforms)