Make authority.normalize_heading() more defensive, and drop back to a plain (non...

Make authority.normalize_heading() more defensive, and drop back to a plain (non-unique) index

NOTE: Database server now requires UUID::Tiny CPAN module in its Perl repertoire

When faced with terrible input, authority.normalize_heading() will generate a
heading based on the MD5 UUID of the input value, flagged with "BAD_MARCXML"
if the MARCXML could not be parsed, or "NOHEADING" if there was no 1xx field.
Previously, authority.normalize_heading() would throw raw, ugly Perl errors.

Many thanks to Mike Rylander and Galen Charlton for their suggestions on how
to break the original version of authority.normalize_heading(), this code
should be much more robust as a result.

git-svn-id: svn://svn.open-ils.org/ILS/trunk@17714 dcc99617-32d9-48b4-a31d-7c20da2025e4