Bug 23416: Add PreserveSerialNotes system preference

Bug 23416: Add PreserveSerialNotes system preference

Bug 11492 intended to pass routinglists forward. It also passed forward serial notes.
This may or not me desired behvaiour, to avoid changing functionality twice I add a syspref
to control this behaviour.

To test:
 1 - Have or create a subscription in the serials module
 2 - Recieve an issue, making sure ot ad a note
 3 - Go to receive again, note the note from the last serial is set for the expected issue
 4 - Apply patch
 5 - Update database, restart all the things
 6 - Receive the issue leaving the note in place
 7 - Note the next expected issue has the note
 8 - Find the syspref PreserveSerialNotes
 9 - Confirm it defaulted to Do
10 - Set it to 'Do not'
11 - Receive the expected serial leavign the note
12 - Note the newly generated expected serial has no note
13 - prove -v t/db_dependent/Serials.t

Signed-off-by: Nadine Pierre <nadine.pierre@inLibro.com>
Signed-off-by: Maryse Simard <maryse.simard@inlibro.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>