Allow numeric indexing in MVVM

[johnwduggan]

Summary of Changes

Adds the ability to handle numeric indices in MVVM.

Checklist

• The PR has a clear and concise title
• Code is self-documented and follows style guidelines.
• Automated tests are written and pass successfully.
• Regression tests (e.g. manually triggered system tests, manual GUI/tool tests, ...) are performed to make sure the PR does not break anything (when applicable)
• Readme file is present and up-to-date.

Documentation Updates

Additional Notes

[SergeyYakubov]

can you add some comments, the code gets hard to read/understand. I know, I should be doing that as well :)