add VersionNumFromSemver for builds

[zackattack01]

This builds on the existing VersionNum logic to add an additional VersionNumFromSemver utility function. While VersionNum works well when the version is known at build time, our build process also needs to be able to use this functionality without setting the required version value for building this package. To support both cases, VersionNumFromSemver will use identical logic, but allow passing in a semver string instead of relying on the internal version variable value