Bug 22818: Add generation and sending of notices

Bug 22818: Add generation and sending of notices

This patch adds the ability for ILL to send notices, both triggered by
staff and triggered by events.

Staff can trigger notices to patrons from the "Manage ILL request" screen:
- ILL request ready for pickup
- ILL request unavailable
- Place request with partners

The following notices to staff are triggered automatically:
- Request has been modified by patron
- Request has been cancelled by patron

Branches can now specify an "ILL email" address to which notices
intended to inform staff of changes to requests by patrons can be sent.

The sending of notices is controlled by a few new sysprefs:
- "ILLDefaultStaffEmail" - Fallback email address for staff ILL notices
to be sent to in the absence of a branch address
- "ILLSendStaffNotices" - To specify which staff notices should be sent
automatically when requests are manipulated by patrons

Patron notices are also controlled by the patron's messaging
preferences

Sponsored-by: PTFS Europe
Signed-off-by: Niamh Walker-Headon <Niamh.Walker-Headon@it-tallaght.ie>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>