Add module to assess demographic and clinical summary stats by predicted ancestry

[rjcorb]

Purpose/implementation Section

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Reproducibility Checklist

• The dependencies required to run the code in this pull request have been added to the
  project Dockerfile.
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Documentation Checklist

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[jharenza]

Still no openxlsx in the docker file, and can you please add a run script to the demo-clin-stats module?

Otherwise, this runs once installed and the simulated p values are very similar, as expected.