Bug 33806: Retain specified date when confirming item parts at checkin

Bug 33806: Retain specified date when confirming item parts at checkin

This patch simply adds hidden inputs to the item parts confirm form
to ensure specified checkin date is retained

To test:
 1 - Find or add an item with subfield 3 - materials specified
 2 - Enable system preference CircConfirmItemParts
 3 - Go to Circulation->Checkin
 4 - Click the settings button in the input box and enter a checkin date and select the remeber check box
 5 - Check in some items, confirm date retained
 6 - Checkin the item with the materials specified
 7 - Confirm checkin
 8 - Note that checkin date is cleared
 9 - Apply patch
10 - Repeat 3-7
11 - Confirm date is retained

Signed-off-by: Andrew Fuerste-Henry <andrewfh@dubcolib.org>
Signed-off-by: Sam Lau <samalau@gmail.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>