Bug 8002 [SIGNED-OFF][REVISED] Can't add patron attribute type in newer installation

Bug 8002 [SIGNED-OFF][REVISED] Can't add patron attribute type in newer installation

Correcting patron_attributes_types definition in kohastructure.sql
to allow NULL entries for category_code, matching the definition
specified in updatedatabase.pl. Adds an entry to updatedatabase.pl
to correct existing installations with the incorrect table structure.

After running the updated updatedatabase.pl the category_code
column in borrower_attribute_types should show that it allows
NULL entries. Adding a new patron attribute type with no
patron category specified should work correctly.

To test the update to kohastructure.sql: Back up your Koha
database, drop it, and recreate it. Load the staff interface
and go through the web installer. After recreating the database
enable ExtendedPatronAttributes and try adding a new patron
attribute type with no patron category specified. The operation
should be successful.

signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
a new update for installations affected.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>