add version, cardinality and occurence(required, optional) to the OGD_AT field description
add version, cardinality and occurence(required, optional) to the OGD_AT field description

Also add a NewBeschreibung method and geters for version and occurence, as these fields are not officially part of the OGDAT-Beschreibung

the42/ogdat,the42/ogdat,the42/ogdat