#1485 (issuing rules improvement) continued

#1485 (issuing rules improvement) continued

IMPORTANT NOTE : all existing test database for 3.0 must manually delete ALL constraints on issuingrules table
(the update22to30.pl don't contain the constraints anymore, as kohastructure.sql, so are concerned only the existing 3.0 tests databases)

Filling issuingrules table :
- the issuingrules table can't have a constraint on categorycode, as we have a '*' categorycode (=default issuingrule)
- reintroducing the "default" issuingrule column
- changing some text ('*' replaced by something more explanatory)
- handling correctly the '0' (that is different from 'undefined'

Signed-off-by: Chris Cormack <crc@liblime.com>
Signed-off-by: Joshua Ferraro <jmf@liblime.com>