Bug5063: C4::Bookseller Changes

Bug5063: C4::Bookseller Changes

Merge unfao changes to C4::Bookseller
Enable warnings in Bookseller.pm
Some cleanups in Bookseller code
Do not export everything by default
Display vendors more rationally
    Was displaying by id make it name as the searchstring is for all
    embedded substrings
Have removed "if mysql" logic as we want to deal with this by
    abstracting the DB interaction and it makes cleaner code until then

Sponsered by UN FAO, Rome

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>