The name of the directory in the expanded artifact (e.g. if it's a tar.gz file then the name of
the directory within it). If no value is known, the defaultVal will be returned.
This can return null if the artifact is not an archive (and if defaultVal is null).
TODO The driver needs to know what will happen when an install archive is unpacked (e.g. an
AS7 install tgz may be automatically expanded into a directory named "jboss-as-7.1.1-FINAL").
However, it's unclear where the best place to encode that is. The driver supplying the default