Bug 7178: Acquisition item creation improvement

Bug 7178: Acquisition item creation improvement

- Display a unique item block at once

On orderreceive.pl when AcqCreateItem is 'receiving', and on
neworderempty.pl when AcqCreateItem is 'ordering' it displays an
item block with item infos to fill, and a '+' button.
When user clicks on '+', the block is hidden and a list shows up with
the items that will be received. User can then edit or delete items in
the list and click 'Save' to receive items.

- PrepareItemrecordDisplay is now used for cloning block

Previous cloning function was duplicating ids, the side effect is that
plugins didn't work when several items were displayed.
PrepareItemrecordDisplay regenerate the form with new ids

- New system preference UniqueItemFields

Contains a space-separated list of sql column names (of items table).
This syspref is used in two ways:
 - Values corresponding to fields in syspref are not duplicated when
   adding a new item (button 'Add')
 - When saving the form, a check is made on fields in syspref for
   detecting duplicate (in DB and in the form)

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
All tests done are noted on the bug report.

2012-03-23: Fixed conflict in updatedatabase.
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>