Bug 23773: Send membership expiry notices by sms too

Bug 23773: Send membership expiry notices by sms too

Test plan:
1. Verify in "About" page that SMS::Send is installed.
   If not, install it.
2. Set system preferences:
   - SMSSendDriver = 'Test'
   - MembershipExpiryDaysNotice = 30
3. In "Notices and Slips" tool, edit the 'MEMBERSHIP_EXPIRY' letter and
   verify that both email and sms parts are filled. Use a different
   title and body for the sms part
4. Create a new borrower with an email address and an SMS number. Set
   their expiry date to a date next week
5. Run misc/cronjobs/membership_expiry.pl --confirm
6. Verify in the patron "Notices" tab that two notices are pending, one
   for email, one for sms

Sponsored-by: Médiathèque de Montauban
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>