Bug 11446: Use encodeURIComponent on search terms in authority lookup plugin

Bug 11446: Use encodeURIComponent on search terms in authority lookup plugin

While adding the data from the existing field to the auth_finder URI,
we're using encodeURI(), which is meant for an entire URI and thus
doesn't escape &. Things that are going into a querystring need
encodeURIComponent() instead.

Test plan:

1. Enable the system preference EnableAdvancedCatalogingEditor
2. Clear your browser cache, even a shift+reload won't get you a fresh
marc-editor.js for the advanced editor
3. Create a Topical Term authority with 150 $aThis & That$xStuff & Junk
4. In the Basic editor, use the authority plugin on the 650 field to
select that authority.
5. Click the authority plugin again, verify that the popup contains This
& That and Stuff & Junk rather than just This and Stuff
6. From the Cataloging home page choose Advanced editor
7. In a new line paste 650 _ _ ‡aThis & That‡xStuff & Junk
8. Type ctrl+shift+L and verify the popup shows both words in both
fields
9. When you remember the plugin exists there too, edit your
Stuff & Junk authority, and in a 550 tag type One & Two in
$a and Three & Four in $x and click the plugin link, verify that
the search window has your search terms not cut off.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>