Bug 31564: Pass start label in PDF link

Bug 31564: Pass start label in PDF link

To test:
1 - Tools->Lbel creator
2 - Make a new batch
3 - Add an item
4 - Click 'export' on the single item
5 - Enter a starting label position greater than 1
6 - Click Export
7 - Click Download as PDF
8 - Note label in 1st position
9 - Apply patch
10 - Repeat and note label position now honored

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>