Bug 10402 follow-up: choose contacts for claims

Bug 10402 follow-up: choose contacts for claims

This patch makes it possible to choose a particular contact for
acquisitions and serials claims. To test:

1) Select a contact to use for claiming late orders and a contact
   to use for claiming late issues.
2) Send a claim for a late order and a claim for a late issue.
3) Note that the claims went out to the proper people.
4) Run the unit test with:
    > prove t/db_dependent/Letters.t
5) Sign off.

Note: the claim messages are recorded in the logs in the *Acquisitions*
module, not the Letters module as you might expect

This patch also fixes several perlcritic violations and centralizes
contact-related unit testing in Bookseller.t.

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>