Squashed commit of the following:

commit c29cd61cf6b1cdc088c26afce51536be2fad2edb
Author: root <root@otrs-dev.(none)>
Date:   Fri Jul 26 16:01:48 2013 +0200

    Fixed a bug that prevented the TicketSearch generic interface connector to work when authenticated as a customer (Cyrille).
Allow TicketSearch GI operation to also work for logged in customers.

This merges https://github.com/OTRS/otrs/pull/86 with slight modifications.