These generic functions return version information for classes
  derived from Versioned-class, or
  VersionsNull-class for unversioned objects. The
  version information is an object of Versions-class.
  By default, classVersion has the following behaviors:
  
    - classVersion(Versioned-instance)
- Returns a Versions-classobject obtained from the object.
    
classVersion{"class"}Consults the definition of class and return the current version information, if available.    
classVersion(ANY)Return a VersionsNull-class object to indicate no version information available.  
  By default, the classVersion<- method has the following behavior:
  
    - classVersion(Versioned-instance)["id"] <- value
- Assign (update or add) valuetoVersions-instance.valueis coerced to a valid version description. seeVersions-classfor additional access methods.