Bug 10012: remove last traces of NoZebra

Bug 10012: remove last traces of NoZebra

This patch removes the last traces of NoZebra:

[1] The DBIC schema class for the nozebra table
[2] References to the NoZebra and NoZebraIndexes sysprefs
    in the Italian SQL scripts.
[3] Deleting the NoZebraIndexes syspref if it's still present.

To test:

[1] Verify that after applying the patch and running the DB upgrade,
    that "NoZebraIndexes" is no longer to be found in the
    systempreferences table.
[2] Verify that "nozebra" is not referenced anywhere in the source
    code except for the database update scripts.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: wajasu <matted-34813@mypacks.net>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>