API version checking for cohort subsets

[azimov]

When we develop new features for Cohort Subset operations older versions of this package will be unable to reference/load many of these properties and crash. Instead, we should perform a version check on the package and store a version reference in the json subset definitions to compare.

There will be updates to this package that do not touch subsets so it may be desirable to specify a minimum version reference in the definition rather than always erroring/warning when a user's package is outdated.

We should also consider tagging subset designs completed in develop branch.