Measure info for dist files

[DanWeinberger]

Ideally there would be a way to track the origin of variables in the dist file more specifically though. In the demo there are examples of inheriting info from other variables at least: https://github.com/DISSC-yale/pophive_demo/blob/main/data/bundle_respiratory/measure_info.json

[miserman]

The new mechanisms to document tall files should cover this: DISSC-yale/dcf#4