Bug 9282: improve auto-completion for authority record finder

Bug 9282: improve auto-completion for authority record finder

This patch adjusts the auto-completion on the authority record
finder (accessed from the bib editor) so that if you do
start typing in the "Main entry ($a only)" input field, it will
return only the $a of the main heading for matching authority
records.

This fixes a problem where typing "shakes", choosing
"Shakespeare, William, 1564-1616" from the auto-completion
result list, then hitting the search button fails to bring
up results, as the dates come from the $d of the 100 field
(in MARC21).

Signed-off-by: Mathieu Saby <mathieu.saby@univ-rennes2.fr>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Works as advertised.
Tested with an authority where I added my search term in $b.
The modified authority came up in main entry, not in mainmainentry.
That was the desired result.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>