Bug 11441: enhance remove_unused_authorities.pl ability to select records

Bug 11441: enhance remove_unused_authorities.pl ability to select records

remove_unused_authorities.pl previously required that --aut be supplied
to specify one or more authority types to check for unlinked authority
records.  If --aut was omitted, it would default to search for
records of authority type NC, which is not present in many (or any?)
Koha databases.

Now, if --aut is omitted, unlinked authority records of any type
are removed.

To test it:
	Parse only PERSO_NAME authorities:
		misc/migration_tools/remove_unused_authorities.pl -aut PERSO_NAME

	Parse all authorities:
		misc/migration_tools/remove_unused_authorities.pl

Signed-off-by: Nicolas Legrand <nicolas.legrand@bulac.fr>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 0f6652d62bd9053c87de5b94eb6a35f68a3af4bf)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>