Bug 14647: (follow-up) Changes to script

Bug 14647: (follow-up) Changes to script

This patch adds the necessary changes to the script so that the filename
extensions works for exporting authorities.

To test:
1) Attempt to export with all filetypes for biblios and authorities
2) Confirm the extension for the exported file (after clicking the
    Export button) is correct for each one

Sponsored-by: Catalyst IT
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>