[CORE-340] update rawls model

[kevinmarete]

https://broadworkbench.atlassian.net/browse/CORE-340
Updating rawls model after broadinstitute/rawls#3205

PR checklist

• For each library you've modified here, decide whether it requires a major, minor, or no version bump. (Click here for guidance)

If you're doing a major or minor version bump to any libraries:

• Bump the version in project/Settings.scala createVersion()
• Update CHANGELOG.md for those libraries
• I promise I used @deprecated instead of deleting code where possible

In all cases:

• Replace the appropriate version hashes in README.md and the CHANGELOG.md for any libs you changed with TRAVIS-REPLACE-ME to auto-update the version string
• Get two thumbsworth of PR review
• Verify all tests go green (CI and coverage tests)
• Squash commits and merge to develop
• Delete branch after merge

[davidangb]

one nit inline, else 👍

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 24.48%. Comparing base (fdb7b18) to head (b7e92ae).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1725   +/-   ##
========================================
  Coverage    24.48%   24.48%           
========================================
  Files          105      105           
  Lines         2745     2745           
  Branches       253      253           
========================================
  Hits           672      672           
  Misses        2073     2073           

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