#15 Non standard GEDCOM xref requirement

[Tom Morris]

It appears that the GEDCOM validation routine used by
the GEDCOM import requires that all level 0 records
have a xref identifier. This identifier is explicitly
identified as being optional in the GEDCOM 5.5 spec, so
this is a stricter requirement than the spec imposes
and thus is unlikely to be met by all applications.

If the database requires an xref identifier, it should
generate one if this optional field is missing.