add Dockerfile and readme for PPP for openmc workflow + fix issue20

[qingfengxia]

3 commits remove all outdated Dockerfiles (keep 1 in the future) add Dockerfile and readme for PPP for openmc workflow fix issue20 set a big ZERO_THRESHOLD for goemetry hash calc

Checklist

• [x] Source is rebased on latest upstream main so is mergeable automatically or easily merged even with confliction.
• [x] Title of this PR is meaningful: e.g. "fix issue #8 geomPipeline.py -o does not work", not "fix geomPipeline.py"
• [x] Commit message is meaningful: git push origin +your_branch to squash some tiny fixes for CI failures
• [x] Give the maintainer the legal rights to change the open source license in the future (see wiki/Contribution.md) for details

[qingfengxia]

John, I will leave you to do the merge, to see if you have been assigned the previledge to do so