Serials updates to link item record to serial table.

Serials updates to link item record to serial table.

This commit makes db changes to subscription, serials tables:
  allow subscriptions larger than 127 issues
  link serial to item uniquely.
MARC Framework:
  Adding MARC tag 942$s (990$s unimarc) to map biblio.serial
Udate biblio.serial on new-subscription.
Use biblio.serial to check if Items.pm should return
  pubdate and enumeration text string from serials table with items.
Update opac-detail so serial items are sorted most recent first.
Adding link from items table to serial table.

Allows sorting of serials in details pages, and removes
enum data from itemnotes field.
Also fixes  visibility in serials item editor

Signed-off-by: Joshua Ferraro <jmf@liblime.com>