code: public final GedObject create(final GedObject parent, final String xref,
              final String tag, final String tail) {
          return getFactory(tag).create(parent, new ObjectId(xref),
                  fullstring(tag), tail);
      }
docs: Factory method creates the appropriate GedObject from the provided
  strings.
  
  @param parent the parent GedObject
  @param xref an optional ID string
  @param tag the GEDCOM tag
  @param tail the rest of the line
  @return the GedObject