Bug 13379: Extends authorised_values.category to varchar(32)

Bug 13379: Extends authorised_values.category to varchar(32)

This patch does 2 things:
1/ It fixes a bug caused by the different data fields used for
authorised_values.category and
borrower_attribute_types.authorised_value_category (varchar(16) vs
varchar(10)).
To reproduce:
- Create a AV category with a length > 10
- Try to link a patron attribute type with this AV, it won't work.

2/ Extends this field to varchar(32): sometime 16 is not enough to
describe something

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
No koha-qa errors. Error reproduced, fixed by patch.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>