Models a version number
Superclass: end
instances of this structure represent a version.
A version consists of a major, minor and a build number. The build number
increases with each build and snapshot of the artefact. "minor" increases
for each shipment and only, if the shipment is not compatible with
the previous version. If "minor" increases this has no effect on "build" .
"major" increases for each release being shipped. In such a case "minor"
and "build" reset to 0.