It will be reused by other DAOs. The class name for PDO::FETCH_CLASS
is now passed as a parameter.

The declaration in CustomerDAO was shadowed by the one in
PostgreSQLCustomerDAO, it was actually invalid because it was declared
"protected", which didn't allow the DAOFactory to instantiate it.

The query for getAll when $active is set was incorrect, so it has been
changed. The front end is not using it, but it can be tested calling
web/services/getUserCustomersService.php?active=true

CustomerVO property names changed for PDO::FETCH_CLASS to work.

The query was incorrect and we hadn't noticed because it's not
currently used by our front end. It can be tested calling
web/services/getUserCustomersService.php?uid=admin&active=true

It was only used from SectorDAO::GetCustomers, which was in turn
unused.

We also remove unnecessary checks for the customer id in update and
delete operations.

Fixes:
* Undefined index: sid, uid, active, login, order
* Undefined variable: string