Bug 31286: Embed see-from headings into bibliographic records export

Bug 31286: Embed see-from headings into bibliographic records export

In misc/export_records.pl add an option to add see-from headings (from authorities 4xx) into bibliographic records export.
Like it is done during record indexing.

Test plan :
1) Choose a biblio record having a field (for example 650) linked to an authority with a see-form.
2) Export this record without see-from headings :
   misc/export_records.pl --starting_biblionumber=X --ending_biblionumber=X --filename /tmp/record_without.xml --format xml
3) Export this record with see-from headings :
   misc/export_records.pl --starting_biblionumber=X --ending_biblionumber=X --filename /tmp/record_with.xml --format xml --embed_see_from_headings
4) Compare /tmp/record_without.xml and /tmp/record_with.xml
=> you should see two 650, one with main heading and one with see-from heading

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>