Bug 14399: Numerous small refinements to the inventory script

Bug 14399: Numerous small refinements to the inventory script

This patch contains the following changes:

[01] Label "Inventory date" reworded to "Last inventory date", adding a
small explanation for its purpose.
[02] Restructured the results: it was an array with items and possible
error messages. Multiple messages duplicated individual items. Now the
results are in a hash, pulling all error messages for one item together.
At the end of the script they are copied to an array. (A helper sub
additemtoresults is added in this regard.) We no longer use array
@items_with_problems.
[03] Both datepickers are no longer connected to the same class. This
prevents changing the set date by filling the last inventory date.
[04] Input markseen in the template and $markseen in the script are
no longer needed.
[05] The paragraph before the detail link in the results table in the
Title column has been removed. Same for problems column. This makes
vertical spacing consistent.
[06] Problem status 'missingitem' is no longer used; the missing items
are marked as 'not_scanned'. Two additional statuses are: no_barcode and
checkedout.
[07] Removed unused $itemtype, $totalrecords and $count. We use variable
$moddatecount to report a count to the template.
[08] The script updated scanned items twice. The first time with ModItem
and the second time with ModDateLastSeen. The second call is removed.
[09] If a book is checked in, we do no longer return an error message when
the checkin is successful (ERR_ONLOAN_RET). The updated datelastseen is
passed to the results.
[10] $wrongplacelist is renamed to $rightplacelist. It is only built when
we need it. (Same for inventorylist now.)
[11] Datelastseen (last inventory date) is always used for building the
inventory list. It allows you to process partial barcode lists or make
a list of items not seen after some date. We do no longer use variable
$paramdatelastseen.
[12] The section where items.datelastseen was compared with the inventory
date has been removed. Scanned items were already updated; to get items
seen before some date, you can now use last inventory date without passing
barcodes.

The form can mainly be used for the following three cases:
[1] Prepare an inventory list or csv file; we do not upload barcodes.
[2] Update items for uploaded barcodes without comparing to inventory.
    Last inventory date is useless in this case.
    Errors wrongplace, checkedout and changestatus are reported.
    Use this scenario for partial scanned barcode lists (all but last).
[3] Update items for uploaded barcodes and compare to inventory, filtered
    by an optional last inventory date.
    Apart from the errors mentioned under [2], this also reports
    not_scanned ("missing") and no_barcode.
    Use this scenario too for the last partial barcode file (together with
    inventory date).

Test plan:
See next patch ("Interface changes").

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>